10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

☒QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2019

or

☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                    to                    

Name of Registrant, State of Incorporation, Address of Principal Executive Offices, Telephone Number, Commission File Number, IRS Employer Identification Number

ALLIANT ENERGY CORPORATION

(a Wisconsin Corporation)

4902 N. Biltmore Lane

Madison, Wisconsin 53718

Telephone (608) 458-3311

Commission File Number - 1-9894

IRS Employer Identification Number - 39-1380265

INTERSTATE POWER & LIGHT COMPANY

(an Iowa corporation)

Alliant Energy Tower

Cedar Rapids, Iowa 52401

Telephone (319) 786-4411

Commission File Number - 1-4117

IRS Employer Identification Number - 42-0331370

WISCONSIN POWER & LIGHT COMPANY

(a Wisconsin corporation)

4902 N. Biltmore Lane

Madison, Wisconsin 53718

Telephone (608) 458-3311

Commission File Number - 0-337

IRS Employer Identification Number - 39-0714890

This combined Form 10-Q is separately filed by Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company. Information contained in the Form 10-Q relating to Interstate Power and Light Company and Wisconsin Power and Light Company is filed by each such registrant on its own behalf. Each of Interstate Power and Light Company and Wisconsin Power and Light Company makes no representation as to information relating to registrants other than itself.

Securities registered pursuant to Section 12(b) of the Act:

Alliant Energy Corporation, Common Stock, $0.01 Par Value, Trading Symbol LNT, Nasdaq Global Select Market

Interstate Power and Light Company, 5.100% Series D Cumulative Perpetual Preferred Stock, $0.01 Par Value, Trading Symbol IPLDP, Nasdaq Global Select Market

Indicate by check mark whether the registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days.

Alliant Energy Corporation - Yes ☒ No ☐

Interstate Power and Light Company - Yes ☒ No ☐

Wisconsin Power and Light Company - Yes ☒ No ☐

Indicate by check mark whether the registrants have submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrants were required to submit such files).

Alliant Energy Corporation - Yes ☒ No ☐

Interstate Power and Light Company - Yes ☒ No ☐

Wisconsin Power and Light Company - Yes ☒ No ☐

Indicate by check mark whether the registrants are large accelerated filers, accelerated filers, non-accelerated filers, smaller reporting companies, or emerging growth companies. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Alliant Energy Corporation - Large Accelerated Filer ☒ Accelerated Filer ☐ Non-accelerated Filer ☐ Smaller Reporting Company ☐ Emerging Growth Company ☐

Interstate Power and Light Company - Large Accelerated Filer ☐ Accelerated Filer ☐ Non-accelerated Filer ☒ Smaller Reporting Company ☐ Emerging Growth Company ☐

Wisconsin Power and Light Company - Large Accelerated Filer ☐ Accelerated Filer ☐ Non-accelerated Filer ☒ Smaller Reporting Company ☐ Emerging Growth Company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.

Alliant Energy Corporation ☐

Interstate Power and Light Company ☐

Wisconsin Power and Light Company ☐

Indicate by check mark whether the registrants are shell companies (as defined in Rule 12b-2 of the Exchange Act).

Alliant Energy Corporation - Yes ☐ No ☒

Interstate Power and Light Company - Yes ☐ No ☒

Wisconsin Power and Light Company - Yes ☐ No ☒

Number of shares outstanding of each class of common stock as of September 30, 2019:

Alliant Energy Corporation, Common Stock, $0.01 par value, 240,342,949 shares outstanding

Interstate Power and Light Company, Common Stock, $2.50 par value, 13,370,788 shares outstanding (all outstanding shares are owned beneficially and of record by Alliant Energy Corporation)

Wisconsin Power and Light Company, Common Stock, $5 par value, 13,236,601 shares outstanding (all outstanding shares are owned beneficially and of record by Alliant Energy Corporation)

TABLE OF CONTENTS

	Page
Definitions	1
Forward-looking Statements	1
Part I. Financial Information	3
Item 1. Condensed Consolidated Financial Statements (Unaudited)	3
Alliant Energy Corporation	3
Interstate Power and Light Company	6
Wisconsin Power and Light Company	9
Combined Notes to Condensed Consolidated Financial Statements	12
1. Summary of Significant Accounting Policies	12
2. Regulatory Matters	13
3. Receivables	14
4. Investments and Acquisitions	15
5. Common Equity	15
6. Debt	18
7. Leases	19
8. Revenues	20
9. Income Taxes	21
10. Benefit Plans	22
11. Asset Retirement Obligations	23
12. Derivative Instruments	23
13. Fair Value Measurements	24
14. Commitments and Contingencies	26
15. Segments of Business	28
16. Related Parties	29
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations	30
Item 3. Quantitative and Qualitative Disclosures About Market Risk	38
Item 4. Controls and Procedures	38
Part II. Other Information	38
Item 1A. Risk Factors	38
Item 2. Unregistered Sales of Equity Securities and Use of Proceeds	38
Item 6. Exhibits	39
Signatures	39

DEFINITIONS

The following abbreviations or acronyms used in this report are defined below:

Abbreviation or Acronym	Definition	Abbreviation or Acronym	Definition
2018 Form 10-K	Combined Annual Report on Form 10-K filed by Alliant Energy, IPL and WPL for the year ended Dec. 31, 2018	GAAP	U.S. generally accepted accounting principles
AEF	Alliant Energy Finance, LLC	IPL	Interstate Power and Light Company
Alliant Energy	Alliant Energy Corporation	IUB	Iowa Utilities Board
ATC	American Transmission Company LLC	MDA	Management’s Discussion and Analysis of Financial Condition and Results of Operations
ATC Holdings	Interest in American Transmission Company LLC and ATC Holdco LLC	MISO	Midcontinent Independent System Operator, Inc.
Corporate Services	Alliant Energy Corporate Services, Inc.	MWh	Megawatt-hour
DAEC	Duane Arnold Energy Center	N/A	Not applicable
Dth	Dekatherm	Note(s)	Combined Notes to Condensed Consolidated Financial Statements
EGU	Electric generating unit	OPEB	Other postretirement benefits
EPA	U.S. Environmental Protection Agency	PPA	Purchased power agreement
EPS	Earnings per weighted average common share	PSCW	Public Service Commission of Wisconsin
Federal Tax Reform	Tax Cuts and Jobs Act	U.S.	United States of America
Financial Statements	Condensed Consolidated Financial Statements	Whiting Petroleum	Whiting Petroleum Corporation
FTR	Financial transmission right	WPL	Wisconsin Power and Light Company

FORWARD-LOOKING STATEMENTS

Statements contained in this report that are not of historical fact are forward-looking statements intended to qualify for the safe harbors from liability established by the Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified as such because the statements include words such as “may,” “believe,” “expect,” “anticipate,” “plan,” “project,” “will,” “projections,” “estimate,” or other words of similar import. Similarly, statements that describe future financial performance or plans or strategies are forward-looking statements. Such forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those expressed in, or implied by, such statements. Some, but not all, of the risks and uncertainties of Alliant Energy, IPL and WPL that could materially affect actual results include:

• IPL’s and WPL’s ability to obtain adequate and timely rate relief to allow for, among other things, the recovery of and/or the return on costs, including fuel costs, operating costs, transmission costs, environmental compliance and remediation costs, deferred expenditures, deferred tax assets, tax expense, capital expenditures, and remaining costs related to EGUs that may be permanently closed and certain other retired assets, earning their authorized rates of return, and the payments to their parent of expected levels of dividends;

• federal and state regulatory or governmental actions, including the impact of legislation, and regulatory agency orders;

• the impact of customer- and third party-owned generation, including alternative electric suppliers, in IPL’s and WPL’s service territories on system reliability, operating expenses and customers’ demand for electricity;

• the impact of energy efficiency, franchise retention and customer disconnects on sales volumes and margins;

• the impact that price changes may have on IPL’s and WPL’s customers’ demand for electric, gas and steam services and their ability to pay their bills;

• the ability to utilize tax credits and net operating losses generated to date, and those that may be generated in the future, before they expire;

• the direct or indirect effects resulting from terrorist incidents, including physical attacks and cyber attacks, or responses to such incidents;

• the impact of penalties or third-party claims related to, or in connection with, a failure to maintain the security of personally identifiable information, including associated costs to notify affected persons and to mitigate their information security concerns;

• employee workforce factors, including changes in key executives, ability to hire and retain employees with specialized skills, ability to create desired corporate culture, collective bargaining agreements and negotiations, work stoppages or restructurings;

• weather effects on results of utility operations;

1

• issues associated with environmental remediation and environmental compliance, including compliance with all environmental and emissions permits, the Coal Combustion Residuals Rule, future changes in environmental laws and regulations, including the EPA’s regulations for carbon dioxide emissions reductions from new and existing fossil-fueled EGUs, and litigation associated with environmental requirements;

• the ability to defend against environmental claims brought by state and federal agencies, such as the EPA, state natural resources agencies or third parties, such as the Sierra Club, and the impact on operating expenses of defending and resolving such claims;

• continued access to the capital markets on competitive terms and rates, and the actions of credit rating agencies;

• inflation and interest rates;

• the impact of the economy in IPL’s and WPL’s service territories and the resulting impacts on sales volumes, margins and the ability to collect unpaid bills;

• the ability to complete construction of wind projects within the cost caps set by regulators and to meet all requirements to qualify for the full level of production tax credits;

• changes in the price of delivered natural gas, purchased electricity and coal due to shifts in supply and demand caused by market conditions and regulations;

• disruptions in the supply and delivery of natural gas, purchased electricity and coal;

• changes in the price of transmission services and the ability to recover the cost of transmission services in a timely manner;

• the direct or indirect effects resulting from breakdown or failure of equipment in the operation of electric and gas distribution systems, such as mechanical problems and explosions or fires, and compliance with electric and gas transmission and distribution safety regulations, including regulations promulgated by the Pipeline and Hazardous Materials Safety Administration;

• issues related to the availability and operations of EGUs, including start-up risks, breakdown or failure of equipment, performance below expected or contracted levels of output or efficiency, operator error, employee safety, transmission constraints, compliance with mandatory reliability standards and risks related to recovery of resulting incremental costs through rates;

• impacts that storms or natural disasters may have on Alliant Energy’s, IPL’s and WPL’s operations and recovery of costs associated with restoration activities, or on the operations of Alliant Energy’s investments;

• any material post-closing adjustments related to any past asset divestitures, including the sales of IPL’s Minnesota electric and natural gas assets, and Whiting Petroleum, which could result from, among other things, indemnification agreements, warranties, parental guarantees or litigation;

• Alliant Energy’s ability to sustain its dividend payout ratio goal;

• changes to costs of providing benefits and related funding requirements of pension and OPEB plans due to the market value of the assets that fund the plans, economic conditions, financial market performance, interest rates, life expectancies and demographics;

• material changes in employee-related benefit and compensation costs;

• risks associated with operation and ownership of non-utility holdings;

• changes in technology that alter the channels through which customers buy or utilize Alliant Energy’s, IPL’s or WPL’s products and services;

• impacts on equity income from unconsolidated investments due to further potential changes to ATC’s authorized return on equity;

• impacts of IPL’s future tax benefits from Iowa rate-making practices, including deductions for repairs expenditures, allocation of mixed service costs and state depreciation, and recoverability of the associated regulatory assets from customers, when the differences reverse in future periods;

• the impacts of adjustments made to deferred tax assets and liabilities from changes in the tax laws;

• changes to the creditworthiness of counterparties with which Alliant Energy, IPL and WPL have contractual arrangements, including participants in the energy markets and fuel suppliers and transporters;

• current or future litigation, regulatory investigations, proceedings or inquiries;

• reputational damage from negative publicity, protests, fines, penalties and other negative consequences resulting in regulatory and/or legal actions;

• the effect of accounting standards issued periodically by standard-setting bodies;

• the ability to successfully complete tax audits and changes in tax accounting methods with no material impact on earnings and cash flows; and

• factors listed in MDA and Risk Factors in Item 1A in the 2018 Form 10-K.

Alliant Energy, IPL and WPL each assume no obligation, and disclaim any duty, to update the forward-looking statements in this report, except as required by law.

2

PART I. FINANCIAL INFORMATION

ITEM 1. CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

	For the Three Months						For the Nine Months
	Ended September 30,						Ended September 30,
	2019			2018			2019			2018
	(in millions, except per share amounts)
Revenues:
Electric utility		$915.9			$861.2			$2,350.5			$2,296.2
Gas utility	41.5			44.8			322.5			299.0
Other utility	11.2			12.3			33.2			36.2
Non-utility	21.6			10.3			61.4			29.6
Total revenues	990.2			928.6			2,767.6			2,661.0
Operating expenses:
Electric production fuel and purchased power	218.5			227.8			601.7			639.5
Electric transmission service	127.5			129.1			362.9			375.2
Cost of gas sold	9.1			11.3			151.1			150.0
Other operation and maintenance	173.7			148.4			527.2			468.8
Depreciation and amortization	143.8			129.0			423.6			376.4
Taxes other than income taxes	27.4			26.9			84.3			78.1
Total operating expenses	700.0			672.5			2,150.8			2,088.0
Operating income	290.2			256.1			616.8			573.0
Other (income) and deductions:
Interest expense	68.3			63.3			203.8			183.8
Equity income from unconsolidated investments, net	(11.6		)	(9.8		)	(35.2		)	(41.6		)
Allowance for funds used during construction	(21.9		)	(18.8		)	(65.6		)	(51.8		)
Other	3.7			1.6			11.0			6.0
Total other (income) and deductions	38.5			36.3			114.0			96.4
Income before income taxes	251.7			219.8			502.8			476.6
Income taxes	23.1			11.7			49.4			42.1
Net income	228.6			208.1			453.4			434.5
Preferred dividend requirements of Interstate Power and Light Company	2.6			2.6			7.7			7.7
Net income attributable to Alliant Energy common shareowners		$226.0			$205.5			$445.7			$426.8
Weighted average number of common shares outstanding:
Basic	239.1			235.2			237.7			232.9
Diluted	239.9			235.2			238.2			232.9
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic		$0.95			$0.87			$1.88			$1.83
Diluted		$0.94			$0.87			$1.87			$1.83

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

3

ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

	September 30, 2019		December 31, 2018
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents		$193.7		$20.9
Accounts receivable, less allowance for doubtful accounts	451.5		350.4
Production fuel, at weighted average cost	71.1		61.4
Gas stored underground, at weighted average cost	46.1		49.0
Materials and supplies, at weighted average cost	106.9		101.4
Regulatory assets	76.3		79.8
Prepaid gross receipts tax	30.3		42.2
Other	137.1		80.0
Total current assets	1,113.0		785.1
Property, plant and equipment, net	13,131.1		12,462.4
Investments:
ATC Holdings	309.1		293.6
Other	143.9		137.7
Total investments	453.0		431.3
Other assets:
Regulatory assets	1,763.7		1,657.5
Deferred charges and other	72.6		89.7
Total other assets	1,836.3		1,747.2
Total assets		$16,533.4		$15,426.0

LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt		$656.8			$256.5
Commercial paper	349.6			441.2
Accounts payable	497.7			543.3
Regulatory liabilities	188.9			142.7
Other	389.1			260.4
Total current liabilities	2,082.1			1,644.1
Long-term debt, net (excluding current portion)	5,535.1			5,246.3
Other liabilities:
Deferred tax liabilities	1,703.0			1,603.1
Regulatory liabilities	1,262.1			1,350.5
Pension and other benefit obligations	476.3			509.1
Other	305.6			287.2
Total other liabilities	3,747.0			3,749.9
Commitments and contingencies (Note 14)
Equity:
Alliant Energy Corporation common equity:
Common stock - $0.01 par value - 480,000,000 shares authorized; 240,342,949 and 236,063,279 shares outstanding	2.4			2.4
Additional paid-in capital	2,236.9			2,045.5
Retained earnings	2,739.1			2,545.9
Accumulated other comprehensive income	1.0			1.7
Shares in deferred compensation trust - 385,343 and 384,580 shares at a weighted average cost of $26.52 and $25.60 per share	(10.2		)	(9.8		)
Total Alliant Energy Corporation common equity	4,969.2			4,585.7
Cumulative preferred stock of Interstate Power and Light Company	200.0			200.0
Total equity	5,169.2			4,785.7
Total liabilities and equity		$16,533.4			$15,426.0

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

4

ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

	For the Nine Months
	Ended September 30,
	2019			2018
	(in millions)
Cash flows from operating activities:
Net income		$453.4			$434.5
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	423.6			376.4
Deferred tax expense and tax credits	53.2			62.5
Equity component of allowance for funds used during construction	(46.3		)	(35.5		)
Other	17.1			2.1
Other changes in assets and liabilities:
Accounts receivable	(359.2		)	(325.2		)
Accounts payable	(27.9		)	(47.3		)
Deferred income taxes	45.4			32.7
Other	(50.1		)	(58.0		)
Net cash flows from operating activities	509.2			442.2
Cash flows used for investing activities:
Construction and acquisition expenditures:
Utility business	(1,003.9		)	(1,080.2		)
Other	(71.4		)	(47.8		)
Cash receipts on sold receivables	255.9			337.2
Other	(41.7		)	(24.9		)
Net cash flows used for investing activities	(861.1		)	(815.7		)
Cash flows from financing activities:
Common stock dividends	(252.5		)	(233.3		)
Proceeds from issuance of common stock, net	185.4			191.3
Proceeds from issuance of long-term debt	950.0			1,500.0
Payments to retire long-term debt	(253.5		)	(603.1		)
Net change in commercial paper and other short-term borrowings	(91.6		)	(278.4		)
Other	(11.7		)	10.9
Net cash flows from financing activities	526.1			587.4
Net increase in cash, cash equivalents and restricted cash	174.2			213.9
Cash, cash equivalents and restricted cash at beginning of period	25.5			33.9
Cash, cash equivalents and restricted cash at end of period		$199.7			$247.8
Supplemental cash flows information:
Cash (paid) refunded during the period for:
Interest		($194.7	)		($171.6	)
Income taxes, net		$0.8			($5.0	)
Significant non-cash investing and financing activities:
Accrued capital expenditures		$254.2			$236.2
Beneficial interest obtained in exchange for securitized accounts receivable		$237.0			$243.7

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

5

INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

	For the Three Months						For the Nine Months
	Ended September 30,						Ended September 30,
	2019			2018			2019			2018
	(in millions)
Revenues:
Electric utility		$560.9			$509.2			$1,373.0			$1,337.0
Gas utility	24.8			26.7			187.8			177.0
Steam and other	10.8			11.7			32.0			34.2
Total revenues	596.5			547.6			1,592.8			1,548.2
Operating expenses:
Electric production fuel and purchased power	126.8			122.5			339.0			354.0
Electric transmission service	91.8			92.8			256.9			268.0
Cost of gas sold	5.9			6.4			80.0			83.8
Other operation and maintenance	100.2			94.6			305.6			297.1
Depreciation and amortization	83.7			73.9			243.4			209.2
Taxes other than income taxes	14.6			14.3			46.4			39.7
Total operating expenses	423.0			404.5			1,271.3			1,251.8
Operating income	173.5			143.1			321.5			296.4
Other (income) and deductions:
Interest expense	31.7			30.4			92.6			90.6
Allowance for funds used during construction	(10.8		)	(11.0		)	(34.5		)	(28.3		)
Other	2.0			0.5			5.4			2.0
Total other (income) and deductions	22.9			19.9			63.5			64.3
Income before income taxes	150.6			123.2			258.0			232.1
Income tax expense (benefit)	6.9			(5.9		)	10.9			(0.5		)
Net income	143.7			129.1			247.1			232.6
Preferred dividend requirements	2.6			2.6			7.7			7.7
Earnings available for common stock		$141.1			$126.5			$239.4			$224.9

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

6

INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

	September 30, 2019		December 31, 2018
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents		$184.0		$9.7
Accounts receivable, less allowance for doubtful accounts	258.3		153.5
Production fuel, at weighted average cost	40.3		44.8
Gas stored underground, at weighted average cost	21.6		26.1
Materials and supplies, at weighted average cost	60.3		55.4
Regulatory assets	34.6		39.2
Other	22.1		43.1
Total current assets	621.2		371.8
Property, plant and equipment, net	7,283.9		6,781.5
Other assets:
Regulatory assets	1,369.4		1,239.8
Deferred charges and other	28.1		18.3
Total other assets	1,397.5		1,258.1
Total assets		$9,302.6		$8,411.4

LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt		$200.0		$—
Commercial paper	—		50.4
Accounts payable	290.0		304.9
Accounts payable to associated companies	40.7		28.8
Regulatory liabilities	95.5		90.0
Accrued taxes	58.7		45.8
Other	197.7		87.2
Total current liabilities	882.6		607.1
Long-term debt, net (excluding current portion)	2,946.8		2,552.3
Other liabilities:
Deferred tax liabilities	974.9		957.3
Regulatory liabilities	638.1		664.9
Pension and other benefit obligations	165.1		178.4
Other	251.0		220.7
Total other liabilities	2,029.1		2,021.3
Commitments and contingencies (Note 14)
Equity:
Interstate Power and Light Company common equity:
Common stock - $2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding	33.4		33.4
Additional paid-in capital	2,322.8		2,222.8
Retained earnings	887.9		774.5
Total Interstate Power and Light Company common equity	3,244.1		3,030.7
Cumulative preferred stock	200.0		200.0
Total equity	3,444.1		3,230.7
Total liabilities and equity		$9,302.6		$8,411.4

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

7

INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

	For the Nine Months
	Ended September 30,
	2019			2018
	(in millions)
Cash flows from operating activities:
Net income		$247.1			$232.6
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	243.4			209.2
Equity component of allowance for funds used during construction	(24.6		)	(19.3		)
Other	(13.2		)	0.7
Other changes in assets and liabilities:
Accounts receivable	(365.0		)	(353.2		)
Accounts payable	(14.0		)	(34.5		)
Deferred income taxes	31.5			22.9
Other	33.3			(19.5		)
Net cash flows from operating activities	138.5			38.9
Cash flows used for investing activities:
Construction and acquisition expenditures	(696.3		)	(635.2		)
Cash receipts on sold receivables	255.9			337.2
Other	(43.7		)	(30.9		)
Net cash flows used for investing activities	(484.1		)	(328.9		)
Cash flows from financing activities:
Common stock dividends	(126.0		)	(125.9		)
Capital contributions from parent	100.0			230.0
Proceeds from issuance of long-term debt	600.0			500.0
Payments to retire long-term debt	—			(100.0		)
Net change in commercial paper	(50.4		)	—
Other	(5.1		)	15.0
Net cash flows from financing activities	518.5			519.1
Net increase in cash, cash equivalents and restricted cash	172.9			229.1
Cash, cash equivalents and restricted cash at beginning of period	12.4			7.2
Cash, cash equivalents and restricted cash at end of period		$185.3			$236.3
Supplemental cash flows information:
Cash (paid) refunded during the period for:
Interest		($93.9	)		($89.1	)
Income taxes, net		$8.2			($2.4	)
Significant non-cash investing and financing activities:
Accrued capital expenditures		$180.2			$142.4
Beneficial interest obtained in exchange for securitized accounts receivable		$237.0			$243.7

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

8

WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

	For the Three Months						For the Nine Months
	Ended September 30,						Ended September 30,
	2019			2018			2019			2018
	(in millions)
Revenues:
Electric utility		$355.0			$352.0			$977.5			$959.2
Gas utility	16.7			18.1			134.7			122.0
Other	0.4			0.6			1.2			2.0
Total revenues	372.1			370.7			1,113.4			1,083.2
Operating expenses:
Electric production fuel and purchased power	91.7			105.3			262.7			285.5
Electric transmission service	35.7			36.3			106.0			107.2
Cost of gas sold	3.2			4.9			71.1			66.2
Other operation and maintenance	62.3			54.2			188.2			172.8
Depreciation and amortization	58.9			54.1			176.6			164.2
Taxes other than income taxes	12.0			11.7			35.4			35.7
Total operating expenses	263.8			266.5			840.0			831.6
Operating income	108.3			104.2			273.4			251.6
Other (income) and deductions:
Interest expense	25.4			24.2			77.3			73.5
Allowance for funds used during construction	(11.1		)	(7.8		)	(31.1		)	(23.5		)
Other	1.4			1.3			4.6			3.4
Total other (income) and deductions	15.7			17.7			50.8			53.4
Income before income taxes	92.6			86.5			222.6			198.2
Income taxes	17.1			10.2			39.4			28.1
Earnings available for common stock		$75.5			$76.3			$183.2			$170.1

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of WPL’s common stock outstanding during the periods presented.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

9

WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

	September 30, 2019		December 31, 2018
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents		$8.3		$8.7
Accounts receivable, less allowance for doubtful accounts	184.3		190.1
Production fuel, at weighted average cost	30.8		16.6
Gas stored underground, at weighted average cost	24.5		22.9
Materials and supplies, at weighted average cost	43.7		42.9
Regulatory assets	41.7		40.6
Prepaid gross receipts tax	30.3		42.2
Other	86.6		20.6
Total current assets	450.2		384.6
Property, plant and equipment, net	5,449.7		5,287.3
Other assets:
Regulatory assets	394.3		417.7
Deferred charges and other	19.5		62.9
Total other assets	413.8		480.6
Total assets		$6,313.7		$6,152.5

LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt		$150.0		$250.0
Commercial paper	—		105.5
Accounts payable	151.1		180.9
Regulatory liabilities	93.4		52.7
Other	113.6		105.5
Total current liabilities	508.1		694.6
Long-term debt, net (excluding current portion)	1,782.3		1,584.9
Other liabilities:
Deferred tax liabilities	652.6		582.0
Regulatory liabilities	624.0		685.6
Finance lease obligations - Sheboygan Falls Energy Facility	53.6		60.0
Pension and other benefit obligations	203.5		217.7
Other	164.8		178.2
Total other liabilities	1,698.5		1,723.5
Commitments and contingencies (Note 14)
Equity:
Wisconsin Power and Light Company common equity:
Common stock - $5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding	66.2		66.2
Additional paid-in capital	1,409.0		1,309.0
Retained earnings	849.6		774.3
Total Wisconsin Power and Light Company common equity	2,324.8		2,149.5
Total liabilities and equity		$6,313.7		$6,152.5

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

10

WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

	For the Nine Months
	Ended September 30,
	2019			2018
	(in millions)
Cash flows from operating activities:
Net income		$183.2			$170.1
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	176.6			164.2
Deferred tax expense and tax credits	54.6			50.3
Other	(7.8		)	(12.0		)
Other changes in assets and liabilities:
Accounts receivable	3.8			29.7
Regulatory liabilities	(28.6		)	7.2
Other	(22.2		)	(64.0		)
Net cash flows from operating activities	359.6			345.5
Cash flows used for investing activities:
Construction and acquisition expenditures	(307.6		)	(445.0		)
Other	(27.3		)	(23.7		)
Net cash flows used for investing activities	(334.9		)	(468.7		)
Cash flows from (used for) financing activities:
Common stock dividends	(107.9		)	(105.0		)
Capital contributions from parent	100.0			200.0
Proceeds from issuance of long-term debt	350.0			—
Payments to retire long-term debt	(250.0		)	—
Net change in commercial paper	(105.5		)	13.4
Other	(10.9		)	(1.7		)
Net cash flows from (used for) financing activities	(24.3		)	106.7
Net increase (decrease) in cash, cash equivalents and restricted cash	0.4			(16.5		)
Cash, cash equivalents and restricted cash at beginning of period	9.2			24.2
Cash, cash equivalents and restricted cash at end of period		$9.6			$7.7
Supplemental cash flows information:
Cash paid during the period for:
Interest		($73.9	)		($68.5	)
Income taxes, net		($7.0	)		($11.2	)
Significant non-cash investing and financing activities:
Accrued capital expenditures		$70.3			$86.2

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

11

ALLIANT ENERGY CORPORATION

INTERSTATE POWER AND LIGHT COMPANY

WISCONSIN POWER AND LIGHT COMPANY

COMBINED NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

NOTE 1(b) Cash and Cash Equivalents - At September 30, 2019, Alliant Energy’s and IPL’s cash and cash equivalents included $174.4 million and $173.7 million of money market fund investments, with interest rates of 2.0% and 2.0%, respectively.

NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

NOTE 1(d) New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

12

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

NOTE 2. REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

Assets Retired Early - Upon completion of the phased installation of advanced metering infrastructure, IPL retired certain analog electric meters in September 2019 and reclassified the $36 million remaining net book value of these meters from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. Recovery of these retired meters is included in the settlement agreement for IPL’s current retail electric base rate increase, and the IUB will decide on the recovery of these assets with the current retail electric rate review decision.

IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by 5 years. The IUB approved placing the buyout payment in a regulatory asset account, which will be recovered from IPL’s retail customers over a 5-year period following the payment. The offsetting obligation has been discounted and is recorded in “Other current liabilities” on Alliant Energy’s and IPL’s balance sheets.

13

Utility Rate Reviews

IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million, on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision.

In October 2019, IPL reached a partial, non-unanimous settlement agreement with intervenor groups for an annual retail electric base rate increase of $127 million. The agreement includes both the recovery of and a return on IPL’s early retired EGUs, and the recovery of IPL’s retired analog electric meters. The settlement agreement also includes IPL providing billing credits over a 12-month period beginning with final rates, including $27 million of excess deferred taxes resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform and $8 million from a partial refund of interim rates implemented in 2019.

The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision, including a decision on the settlement agreement, from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.

IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects. In October 2019, IPL reached a unanimous settlement agreement with intervenor groups for an annual retail gas base rate increase of $12 million. IPL currently expects a decision, including a decision on the settlement agreement, from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.

NOTE 3. RECEIVABLES

Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of September 30, 2019, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Maximum outstanding aggregate cash proceeds		$103.0		$110.0		$108.0		$116.0
Average outstanding aggregate cash proceeds	45.4		36.4		42.9		49.8

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

	September 30, 2019		December 31, 2018
Customer accounts receivable		$154.2		$140.1
Unbilled utility revenues	92.1		97.1
Other receivables	0.4		0.1
Receivables sold to third party	246.7		237.3
Less: cash proceeds	1.0		108.0
Deferred proceeds	245.7		129.3
Less: allowance for doubtful accounts	8.7		9.9
Fair value of deferred proceeds		$237.0		$119.4

14

As of September 30, 2019, outstanding receivables past due under the Receivables Agreement were $26.6 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Collections		$592.2		$549.5		$1,635.7		$1,550.2
Write-offs, net of recoveries	3.2		4.9		11.3		12.9

NOTE 4. INVESTMENTS AND ACQUISITIONS

Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):

	Three Months						Nine Months
	2019			2018			2019			2018
ATC Holdings		($10.5	)		($8.9	)		($30.0	)		($25.4	)
Non-utility wind farm in Oklahoma	(0.4		)	0.1			(2.8		)	(14.5		)
Other	(0.7		)	(1.0		)	(2.4		)	(1.7		)
		($11.6	)		($9.8	)		($35.2	)		($41.6	)

Non-utility Transportation Acquisitions - In the first quarter of 2019, Alliant Energy, through its wholly-owned non-utility subsidiaries, completed acquisitions of freight management companies located in Cedar Rapids, Iowa and Stoughton, Wisconsin. These acquisitions were purchased for $21 million, including contingent consideration of $8 million, which is expected to be paid within two years. The purchase price was largely allocated to intangibles and the remainder was allocated to working capital and property.

NOTE 5. COMMON EQUITY

Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2019	236,063,279
Equity forward agreements	3,790,300
Shareowner Direct Plan	390,630
Equity-based compensation plans	101,478
Other	(2,738	)
Shares outstanding, September 30, 2019	240,342,949

Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. The initial forward sale price of $44.33 per share is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreements. In 2019, Alliant Energy settled $167 million under the forward sale agreements by delivering 3,790,300 shares of newly issued Alliant Energy common stock at a weighted average forward sale price of $43.99 per share. Alliant Energy used the net proceeds from the settlements for general corporate purposes. As of September 30, 2019, 671,237 incremental shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements.

15

Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

16

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

17

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

Comprehensive Income - For the three and nine months ended September 30, 2019 and 2018, Alliant Energy’s other comprehensive income was not material; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three and nine months ended September 30, 2019 and 2018, IPL and WPL had no other comprehensive income; therefore, their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.

NOTE 6. DEBT

NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year, which currently expires in August 2023. As of September 30, 2019, the short-term borrowing capacity under the agreement totaled $1 billion ($450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. In September 2019, IPL issued $300 million of 3.50% senior debentures due 2049. The senior debentures were issued as green bonds, and all of the net proceeds have been or will be allocated for the construction and development of IPL’s wind projects.

In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.

18

NOTE 7. LEASES

Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions):

	September 30, 2019
Property, plant and equipment, net		$34
Other current liabilities		$8
Finance lease obligations - Sheboygan Falls Energy Facility	54
Total finance lease liabilities		$62
Remaining lease term	6 years
Discount rate	11		%
	Three Months Ended			Nine Months Ended
	September 30, 2019			September 30, 2019
Depreciation expense		$1			$4
Interest expense	1			5
Total finance lease expense		$2			$9

Expected Maturities - As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

19

Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

NOTE 8. REVENUES

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

20

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

NOTE 9. INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

21

Deferred Tax Assets and Liabilities -

Carryforwards - At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

NOTE 10. BENEFIT PLANS

NOTE 10(a) Pension and OPEB Plans -

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

As of September 30, 2019, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $7.2 million, $4.0 million and $2.9 million, respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years.

22

For the nine months ended September 30, 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3-year performance period. For the nine months ended September 30, 2019, 91,816 performance shares were granted with a weighted average grant date fair value of $47.23. The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3-year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3-year time-vesting period. For the nine months ended September 30, 2019, 91,816 performance restricted stock units were granted with a weighted average grant date fair value of $46.10, and 105,348 restricted stock units were granted with a weighted average grant date fair value of $45.98, which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of September 30, 2019, 122,720 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

NOTE 11. ASSET RETIREMENT OBLIGATIONS

A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2019 is as follows (in millions):

	Alliant Energy			IPL
Balance, January 1		$177.5			$118.3
Revisions in estimated cash flows	(5.8		)	(7.0		)
Liabilities settled	(5.9		)	(5.6		)
Liabilities incurred (a)	26.2			26.2
Accretion expense	5.3			3.5
Balance, September 30		$197.3			$135.4

(a) During the nine months ended September 30, 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

NOTE 12. DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Notional Amounts - As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

23

Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At September 30, 2019 and December 31, 2018, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at September 30, 2019 and December 31, 2018. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

NOTE 13. FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

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Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

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WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

NOTE 14. COMMITMENTS AND CONTINGENCIES

NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s and WPL’s projects include the expansion of wind generation, and WPL’s projects also include the West Riverside Energy Center. At September 30, 2019, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $124 million, $79 million and $45 million, respectively.

NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

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(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

NOTE 14(c) Guarantees and Indemnifications -

Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of September 30, 2019, the present value of the abandonment obligations is estimated at $38 million. Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of September 30, 2019 and December 31, 2018.

Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $82 million as of September 30, 2019 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of September 30, 2019 and December 31, 2018.

IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of September 30, 2019 and December 31, 2018. The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020.

NOTE 14(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2019, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At September 30, 2019, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$14	-	$31		$12	-	$25
Current and non-current environmental liabilities	19				16

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.

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Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act.

Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters.

NOTE 14(e) Collective Bargaining Agreements - At September 30, 2019, employees covered by collective bargaining agreements represented 54%, 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. In November 2019, the parties reached a new agreement, which expires May 31, 2022.

NOTE 15. SEGMENTS OF BUSINESS

Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations.

										ATC Holdings,		Alliant
	Utility									Non-Utility,		Energy
	Electric		Gas			Other		Total		Parent and Other		Consolidated
	(in millions)
Three Months Ended September 30, 2019
Revenues		$915.9		$41.5			$11.2		$968.6		$21.6		$990.2
Operating income (loss)	283.7		(4.7		)	2.8		281.8		8.4		290.2
Net income attributable to Alliant Energy common shareowners								216.6		9.4		226.0
Three Months Ended September 30, 2018
Revenues		$861.2		$44.8			$12.3		$918.3		$10.3		$928.6
Operating income (loss)	248.7		(2.0		)	0.6		247.3		8.8		256.1
Net income attributable to Alliant Energy common shareowners								202.8		2.7		205.5

									ATC Holdings,		Alliant
	Utility								Non-Utility,		Energy
	Electric		Gas		Other		Total		Parent and Other		Consolidated
	(in millions)
Nine Months Ended September 30, 2019
Revenues		$2,350.5		$322.5		$33.2		$2,706.2		$61.4		$2,767.6
Operating income	543.0		47.7		4.2		594.9		21.9		616.8
Net income attributable to Alliant Energy common shareowners							422.6		23.1		445.7
Nine Months Ended September 30, 2018
Revenues		$2,296.2		$299.0		$36.2		$2,631.4		$29.6		$2,661.0
Operating income	510.2		34.9		2.9		548.0		25.0		573.0
Net income attributable to Alliant Energy common shareowners							395.0		31.8		426.8

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IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations.

	Electric		Gas			Other		Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$560.9		$24.8			$10.8		$596.5
Operating income (loss)	175.1		(4.2		)	2.6		173.5
Earnings available for common stock								141.1
Three Months Ended September 30, 2018
Revenues		$509.2		$26.7			$11.7		$547.6
Operating income (loss)	144.7		(3.1		)	1.5		143.1
Earnings available for common stock								126.5
Nine Months Ended September 30, 2019
Revenues		$1,373.0		$187.8			$32.0		$1,592.8
Operating income	290.8		26.3			4.4		321.5
Earnings available for common stock								239.4
Nine Months Ended September 30, 2018
Revenues		$1,337.0		$177.0			$34.2		$1,548.2
Operating income	275.7		16.3			4.4		296.4
Earnings available for common stock								224.9

WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations.

	Electric		Gas			Other			Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$355.0		$16.7			$0.4			$372.1
Operating income (loss)	108.6		(0.5		)	0.2			108.3
Earnings available for common stock									75.5
Three Months Ended September 30, 2018
Revenues		$352.0		$18.1			$0.6			$370.7
Operating income (loss)	104.0		1.1			(0.9		)	104.2
Earnings available for common stock									76.3
Nine Months Ended September 30, 2019
Revenues		$977.5		$134.7			$1.2			$1,113.4
Operating income (loss)	252.2		21.4			(0.2		)	273.4
Earnings available for common stock									183.2
Nine Months Ended September 30, 2018
Revenues		$959.2		$122.0			$2.0			$1,083.2
Operating income (loss)	234.5		18.6			(1.5		)	251.6
Earnings available for common stock									170.1

NOTE 16. RELATED PARTIES

Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

29

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
ATC billings to WPL		$28		$26		$82		$79
WPL billings to ATC	3		3		10		8

WPL owed ATC net amounts of $9 million as of September 30, 2019 and $8 million as of December 31, 2018.

WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 7 for discussion of WPL’s Sheboygan Falls Energy Facility lease.

ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

This MDA includes information relating to Alliant Energy, and IPL and WPL (collectively, the Utilities), as well as ATC Holdings, AEF and Corporate Services. Where appropriate, information relating to a specific entity has been segregated and labeled as such. The following discussion and analysis should be read in conjunction with the Financial Statements and the Notes included in this report, as well as the financial statements, notes and MDA included in the 2018 Form 10-K. Unless otherwise noted, all “per share” references in MDA refer to earnings per diluted share.

2019 HIGHLIGHTS

Key highlights since the filing of the 2018 Form 10-K include the following:

Rate Matters:

• In March 2019, IPL filed requests with the IUB to increase annual base rates for its Iowa retail electric and gas customers, which were based on a forward-looking test period that includes 2020. IPL concurrently filed for interim retail electric rates based on a 2018 historical Test Year, which were implemented effective April 1, 2019. In October 2019, IPL reached settlement agreements with intervenor groups for annual retail electric and gas base rate increases. The electric base rate agreement includes a return on common equity of 9.5% for all non-advanced rate making principle generating assets and 5% for production tax credit carryforwards for the most recent 1,000 MW of new wind generation development, recovery of the most recent 1,000 MW of new wind generation development through a new renewable energy rider, and a 51% common equity component of regulatory capital structure. The gas base rate agreement includes a return on common equity of 9.6% and a 51% common equity component of regulatory capital structure. Refer to Note 2 for details.

• In March 2019, the IUB approved IPL’s energy efficiency plan for 2019 through 2023, which provides direct financial savings to customers and provides cost-effective options to help electric and gas customers reduce their energy usage. The energy efficiency costs, which are lower than previous energy efficiency plans, are reflected on electric and gas customer bills beginning June 2019 and November 2019, respectively.

30

Customer Investments:

• In March 2019, IPL placed approximately 470 megawatts of new wind generation in service at the Upland Prairie and English Farms wind sites. IPL’s retail electric customers began to see the rate impacts of this renewable generation with the interim electric rates effective April 1, 2019.

• In January and March 2019, AEF, a subsidiary of Alliant Energy, purchased two freight management companies. These non-utility acquisitions enhance Alliant Energy’s Transportation value to customers by adding customized supply chain solution capabilities to their portfolio of service offerings. Refer to Note 4 for details.

• The installation of a selective catalytic reduction system at IPL’s Ottumwa Unit 1 was completed in the first quarter of 2019, which supports compliance obligations under the Cross-State Air Pollution Rule and IPL’s Consent Decree.

• In September 2019, WPL filed a Certificate of Authority application with the PSCW for approval to expand its gas distribution systems in Western Wisconsin in 2020. Estimated capital expenditures for this project for 2020 are included in the “Gas distribution systems” line in the construction and acquisition expenditures table in “Liquidity and Capital Resources.”

• Alliant Energy’s cleaner energy strategy includes the planned development and acquisition of up to 1,000 MW of solar generation at WPL. Estimated capital expenditures for the planned solar projects for 2021 through 2023 are included in the “Renewable projects” line in the construction and acquisitions table in “Liquidity and Capital Resources.”

Financings and Common Stock Dividends:

• In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. In September 2019, IPL issued $300 million of 3.50% senior debentures due 2049. The senior debentures were issued as green bonds, and all of the net proceeds have been or will be allocated for the construction and development of IPL’s wind projects.

• In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.

• Refer to “Results of Operations” for discussion of expected issuances of common stock and long-term debt in 2020.

RESULTS OF OPERATIONS

Results of operations include financial information prepared in accordance with GAAP as well as utility electric margins and utility gas margins, which are not measures of financial performance under GAAP. Utility electric margins are defined as electric revenues less electric production fuel, purchased power and electric transmission service expenses. Utility gas margins are defined as gas revenues less cost of gas sold. Utility electric margins and utility gas margins are non-GAAP financial measures because they exclude other utility and non-utility revenues, other operation and maintenance expenses, depreciation and amortization expenses, and taxes other than income tax expense.

Management believes that utility electric and gas margins provide a meaningful basis for evaluating and managing utility operations since electric production fuel, purchased power and electric transmission service expenses and cost of gas sold are generally passed through to customers, and therefore, result in changes to electric and gas revenues that are comparable to changes in such expenses. The presentation of utility electric and gas margins herein is intended to provide supplemental information for investors regarding operating performance. These utility electric and gas margins may not be comparable to how other entities define utility electric and gas margin. Furthermore, these measures are not intended to replace operating income as determined in accordance with GAAP as an indicator of operating performance.

Additionally, the table below includes EPS for Utilities and Corporate Services, ATC Holdings, and Non-utility and Parent, which are non-GAAP financial measures. Alliant Energy believes these non-GAAP financial measures are useful to investors because they facilitate an understanding of segment performance and trends, and provide additional information about Alliant Energy’s operations on a basis consistent with the measures that management uses to manage its operations and evaluate its performance.

Financial Results Overview - Alliant Energy’s net income and EPS attributable to Alliant Energy common shareowners for the three months ended September 30, 2019 and 2018 were as follows (dollars in millions, except per share amounts):

	2019						2018
	Income (Loss)			EPS			Income (Loss)			EPS
Utilities and Corporate Services		$219.6			$0.92			$206.3			$0.88
ATC Holdings	7.9			0.03			6.3			0.03
Non-utility and Parent	(1.5		)	(0.01		)	(7.1		)	(0.04		)
Alliant Energy Consolidated		$226.0			$0.94			$205.5			$0.87

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Alliant Energy’s Utilities and Corporate Services net income increased by $13 million for the three-month period, primarily due to higher earnings resulting from IPL’s and WPL’s increasing rate base and timing of income tax expense. These items were partially offset by higher depreciation expense.

For the three and nine months ended September 30, operating income and a reconciliation of utility electric and gas margins to the most directly comparable GAAP measure, operating income, was as follows (in millions):

	Alliant Energy						IPL						WPL
Three Months	2019			2018			2019			2018			2019			2018
Operating income		$290.2			$256.1			$173.5			$143.1			$108.3			$104.2
Electric utility revenues		$915.9			$861.2			$560.9			$509.2			$355.0			$352.0
Electric production fuel and purchased power expenses	(218.5		)	(227.8		)	(126.8		)	(122.5		)	(91.7		)	(105.3		)
Electric transmission service expense	(127.5		)	(129.1		)	(91.8		)	(92.8		)	(35.7		)	(36.3		)
Utility Electric Margin (non-GAAP)	569.9			504.3			342.3			293.9			227.6			210.4
Gas utility revenues	41.5			44.8			24.8			26.7			16.7			18.1
Cost of gas sold	(9.1		)	(11.3		)	(5.9		)	(6.4		)	(3.2		)	(4.9		)
Utility Gas Margin (non-GAAP)	32.4			33.5			18.9			20.3			13.5			13.2
Other utility revenues	11.2			12.3			10.8			11.7			0.4			0.6
Non-utility revenues	21.6			10.3			—			—			—			—
Other operation and maintenance expenses	(173.7		)	(148.4		)	(100.2		)	(94.6		)	(62.3		)	(54.2		)
Depreciation and amortization expenses	(143.8		)	(129.0		)	(83.7		)	(73.9		)	(58.9		)	(54.1		)
Taxes other than income tax expense	(27.4		)	(26.9		)	(14.6		)	(14.3		)	(12.0		)	(11.7		)
Operating income		$290.2			$256.1			$173.5			$143.1			$108.3			$104.2

	Alliant Energy						IPL						WPL
Nine Months	2019			2018			2019			2018			2019			2018
Operating income		$616.8			$573.0			$321.5			$296.4			$273.4			$251.6
Electric utility revenues		$2,350.5			$2,296.2			$1,373.0			$1,337.0			$977.5			$959.2
Electric production fuel and purchased power expenses	(601.7		)	(639.5		)	(339.0		)	(354.0		)	(262.7		)	(285.5		)
Electric transmission service expense	(362.9		)	(375.2		)	(256.9		)	(268.0		)	(106.0		)	(107.2		)
Utility Electric Margin (non-GAAP)	1,385.9			1,281.5			777.1			715.0			608.8			566.5
Gas utility revenues	322.5			299.0			187.8			177.0			134.7			122.0
Cost of gas sold	(151.1		)	(150.0		)	(80.0		)	(83.8		)	(71.1		)	(66.2		)
Utility Gas Margin (non-GAAP)	171.4			149.0			107.8			93.2			63.6			55.8
Other utility revenues	33.2			36.2			32.0			34.2			1.2			2.0
Non-utility revenues	61.4			29.6			—			—			—			—
Other operation and maintenance expenses	(527.2		)	(468.8		)	(305.6		)	(297.1		)	(188.2		)	(172.8		)
Depreciation and amortization expenses	(423.6		)	(376.4		)	(243.4		)	(209.2		)	(176.6		)	(164.2		)
Taxes other than income tax expense	(84.3		)	(78.1		)	(46.4		)	(39.7		)	(35.4		)	(35.7		)
Operating income		$616.8			$573.0			$321.5			$296.4			$273.4			$251.6

Operating Income Variances - Variances between periods in operating income for the three and nine months ended September 30, 2019 compared to the same periods in 2018 were as follows (in millions):

	Three Months									Nine Months
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Total higher utility electric margin variance (Refer to details below)		$66			$48			$17			$104			$62			$42
Total higher (lower) utility gas margin variance (Refer to details below)	(1		)	(1		)	—			22			15			8
Higher non-utility revenues due to AEF’s new acquisitions	10			—			—			31			—			—
Total higher other operation and maintenance expenses variance (Refer to details below)	(25		)	(6		)	(8		)	(58		)	(9		)	(15		)
Higher depreciation and amortization expense, primarily due to additional plant in service in 2018 and 2019 and new IPL depreciation rates effective May 2018	(15		)	(10		)	(5		)	(47		)	(34		)	(12		)
Other	(1		)	(1		)	—			(8		)	(9		)	(1		)
		$34			$30			$4			$44			$25			$22

32

Electric and Gas Revenues and Sales Summary - Electric and gas revenues (in millions), and MWh and Dth sales (in thousands), for the three and nine months ended September 30 were as follows:

Alliant Energy	Electric						Gas
	Revenues				MWhs Sold		Revenues				Dths Sold
	2019		2018		2019	2018	2019		2018		2019	2018
Three Months
Retail		$825.9		$776.1	6,868	6,892		$32.7		$35.8	3,144	3,867
Sales for resale	71.9		70.2		2,003	1,675	N/A		N/A		N/A	N/A
Transportation/Other	18.1		14.9		23	19	8.8		9.0		25,021	23,213
		$915.9		$861.2	8,894	8,586		$41.5		$44.8	28,165	27,080
Nine Months
Retail		$2,109.2		$2,057.4	19,035	19,399		$286.8		$268.8	36,560	35,678
Sales for resale	191.0		198.8		4,835	4,557	N/A		N/A		N/A	N/A
Transportation/Other	50.3		40.0		71	67	35.7		30.2		71,814	67,886
		$2,350.5		$2,296.2	23,941	24,023		$322.5		$299.0	108,374	103,564

IPL	Electric						Gas
	Revenues				MWhs Sold		Revenues				Dths Sold
	2019		2018		2019	2018	2019		2018		2019	2018
Three Months
Retail		$511.9		$467.5	3,827	3,838		$19.5		$21.0	1,644	2,060
Sales for resale	37.8		31.0		1,414	917	N/A		N/A		N/A	N/A
Transportation/Other	11.2		10.7		9	10	5.3		5.7		8,701	8,994
		$560.9		$509.2	5,250	4,765		$24.8		$26.7	10,345	11,054
Nine Months
Retail		$1,247.8		$1,218.4	10,706	11,060		$165.8		$156.8	19,010	18,838
Sales for resale	95.7		91.6		3,241	2,444	N/A		N/A		N/A	N/A
Transportation/Other	29.5		27.0		27	28	22.0		20.2		28,528	28,893
		$1,373.0		$1,337.0	13,974	13,532		$187.8		$177.0	47,538	47,731

WPL	Electric						Gas
	Revenues				MWhs Sold		Revenues				Dths Sold
	2019		2018		2019	2018	2019		2018		2019	2018
Three Months
Retail		$314.0		$308.6	3,041	3,054		$13.2		$14.8	1,500	1,807
Sales for resale	34.1		39.2		589	758	N/A		N/A		N/A	N/A
Transportation/Other	6.9		4.2		14	9	3.5		3.3		16,320	14,219
		$355.0		$352.0	3,644	3,821		$16.7		$18.1	17,820	16,026
Nine Months
Retail		$861.4		$839.0	8,329	8,339		$121.0		$112.0	17,550	16,840
Sales for resale	95.3		107.2		1,594	2,113	N/A		N/A		N/A	N/A
Transportation/Other	20.8		13.0		44	39	13.7			$10.0	43,286	38,993
		$977.5		$959.2	9,967	10,491		$134.7		$122.0	60,836	55,833

Sales Trends and Temperatures - Alliant Energy’s retail electric sales volumes remained unchanged and decreased 2% for the three and nine months ended September 30, 2019 compared to the same periods in 2018, respectively. The decrease for the nine-month period was primarily due to the impact of lower residential and commercial sales due to cooler temperatures during the second quarter of 2019.

Estimated increases to electric and gas margins from the impacts of temperatures for the three and nine months ended September 30 were as follows (in millions):

	Electric Margins														Gas Margins
	Three Months							Nine Months							Three Months						Nine Months
	2019		2018		Change			2019		2018		Change			2019		2018		Change		2019		2018		Change
IPL		$4		$4		$—			$7		$18		($11	)		$—		$—		$—		$4		$1		$3
WPL	2		3		(1		)	2		10		(8		)	—		—		—		2		1		1
Total Alliant Energy		$6		$7		($1	)		$9		$28		($19	)		$—		$—		$—		$6		$2		$4

33

Utility Electric Margin Variances - The following items contributed to increased (decreased) utility electric margins for the three and nine months ended September 30, 2019 compared to the same periods in 2018 as follows (in millions):

	Three Months									Nine Months
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Impact of IPL’s retail electric interim and final base rate increases effective April 2019 and May 2018, respectively (a)		$41			$41			$—			$77			$77			$—
Higher margins at WPL from earning on increasing rate base for rates effective January 2019	16			—			16			42			—			42
Estimated changes in sales volumes caused by temperatures	(1		)	—			(1		)	(19		)	(11		)	(8		)
Higher revenues at IPL due to changes in electric tax benefit rider credits on customers’ bills (offset by changes in income tax expense)	6			6			—			4			4			—
Higher revenues at IPL related to changes in recovery amounts for energy efficiency costs through the energy efficiency rider (mostly offset by changes in energy efficiency expense)	2			2			—			3			3
Other	2			(1		)	2			(3		)	(11		)	8
		$66			$48			$17			$104			$62			$42

(a) IPL’s interim retail electric base rate increase effective April 1, 2019 was reduced by anticipated production tax credits for IPL’s new wind generation placed in service in March 2019. This reduction in revenue requirement is expected to be offset by a reduction in income tax expense resulting from production tax credits recognized from the new wind generation. Additionally, the interim retail electric base rate increase was reduced by $8 million as a result of the partial refund agreed to as part of the rate review proposed settlement. Refer to Note 2 for further discussion.

Utility Gas Margin Variances - The following items contributed to increased (decreased) utility gas margins for the three and nine months ended September 30, 2019 compared to the same periods in 2018 as follows (in millions):

	Three Months									Nine Months
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Impact of IPL’s retail gas final base rate increase effective January 2019		$—			$—			$—			$8		$8		$—
Higher margins at WPL from earning on increasing rate base for rates effective January 2019	1			—			1			6		—		6
Estimated changes in sales volumes caused by temperatures	—			—			—			4		3		1
Higher revenues at IPL related to changes in recovery amounts for energy efficiency costs through the energy efficiency rider (mostly offset by changes in energy efficiency expense)	—			—			—			3		3		—
Other	(2		)	(1		)	(1		)	1		1		1
		($1	)		($1	)		$—			$22		$15		$8

Other Operation and Maintenance Expenses Variances - The following items contributed to (increased) decreased other operation and maintenance expenses for the three and nine months ended September 30, 2019 compared to the same periods in 2018 as follows (in millions):

	Three Months									Nine Months
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Higher operation expense at AEF due to new acquisitions		($10	)		$—			$—			($29	)		$—			$—
Higher energy efficiency cost recovery amortizations at WPL pursuant to authorization from PSCW rate order effective January 2019	(4		)	—			(4		)	(11		)	—			(11		)
Higher energy efficiency expense at IPL (primarily offset by higher gas revenues)	(1		)	(1		)	—			(5		)	(5		)	—
Higher performance compensation expense	(4		)	(2		)	(2		)	(5		)	(2		)	(2		)
Other	(6		)	(3		)	(2		)	(8		)	(2		)	(2		)
		($25	)		($6	)		($8	)		($58	)		($9	)		($15	)

34

Other Income and Deductions Variances - The following items contributed to (increased) decreased other income and deductions for the three and nine months ended September 30, 2019 compared to the same periods in 2018 as follows (in millions):

	Three Months									Nine Months
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Higher interest expense primarily due to higher average outstanding long-term debt balances		($5	)		($1	)		($1	)		($20	)		($2	)		($4	)
Lower equity income due to decreased earnings from non-utility wind farm resulting from an acceleration of earnings in the first quarter of 2018 due to Federal Tax Reform	—			—			—			(12		)	—			—
Higher allowance for funds used during construction primarily due to changes in construction work in progress balances related to IPL’s new wind generation and WPL’s West Riverside Energy Center	3			—			3			14			6			8
Other	—			(2		)	—			—			(3		)	(1		)
		($2	)		($3	)		$2			($18	)		$1			$3

Income Taxes - Refer to Note 9 for details of effective income tax rates.

Other Future Considerations - In addition to items discussed in MDA and the Notes in Item 1, the following key items could impact Alliant Energy’s, IPL’s and WPL’s future financial condition or results of operations:

• Financing Plans - Alliant Energy currently expects to issue up to $250 million of common stock in 2020 through one or more offerings and its Shareowner Direct Plan. IPL, WPL and AEF currently expect to issue up to $300 million, $350 million and $300 million of long-term debt in 2020, respectively. IPL, WPL and AEF have $200 million, $150 million and $300 million of long-term debt maturing in 2020, respectively.

• Common Stock Dividends - Alliant Energy announced a 7% increase in its targeted 2020 annual common stock dividend to $1.52 per share, which is equivalent to a quarterly rate of $0.38 per share, beginning with the February 2020 dividend payment. The timing and amount of future dividends is subject to an approved dividend declaration from Alliant Energy’s Board of Directors, and is dependent upon earnings expectations, capital requirements, and general financial business conditions, among other factors.

• Higher Earnings on Increasing Rate Base - Alliant Energy and IPL currently expect an increase in earnings in 2020 compared to 2019 due to impacts from increasing revenue requirements from IPL’s retail electric and gas rate reviews (2020 Forward-looking Test Period). IPL’s and WPL’s 2020 increased revenue requirements are expected to be offset by returning to customers a portion of the excess deferred income tax credits from Federal Tax Reform.

• Depreciation and Amortization Expenses - Alliant Energy, IPL and WPL currently expect an increase in depreciation and amortization expenses in 2020 compared to 2019 due to property additions, including IPL’s expansion of wind generation and WPL’s West Riverside natural gas-fired EGU.

• Interest Expense - Alliant Energy currently expects interest expense to increase in 2020 compared to 2019 primarily due to financings completed in 2019 and planned in 2020 as discussed above.

• Allowance for Funds Used During Construction - Alliant Energy currently expects allowance for funds used during construction to decrease in 2020 compared to 2019 primarily due to decreased construction work in progress balances related to IPL’s wind generation that was placed in service in 2019 and is expected to be placed in service in 2020, and WPL’s West Riverside Energy Center, which is currently expected to be placed in service by the end of 2019.

LIQUIDITY AND CAPITAL RESOURCES

The liquidity and capital resources summary included in the 2018 Form 10-K has not changed materially, except as described below.

Liquidity Position - At September 30, 2019, Alliant Energy had $194 million of cash and cash equivalents, $650 million ($100 million at the parent company, $250 million at IPL and $300 million at WPL) of available capacity under the single revolving credit facility and $109 million of available capacity at IPL under its sales of accounts receivable program.

35

Capital Structure - Capital structures at September 30, 2019 were as follows (Long-term Debt (including current maturities) (LD); Short-term Debt (SD); Common Equity (CE); IPL’s Preferred Stock (PS)):

Cash Flows - Selected information from the cash flows statements was as follows (in millions):

	Alliant Energy						IPL						WPL
	2019			2018			2019			2018			2019			2018
Cash, cash equivalents and restricted cash, January 1		$25.5			$33.9			$12.4			$7.2			$9.2			$24.2
Cash flows from (used for):
Operating activities	509.2			442.2			138.5			38.9			359.6			345.5
Investing activities	(861.1		)	(815.7		)	(484.1		)	(328.9		)	(334.9		)	(468.7		)
Financing activities	526.1			587.4			518.5			519.1			(24.3		)	106.7
Net increase (decrease)	174.2			213.9			172.9			229.1			0.4			(16.5		)
Cash, cash equivalents and restricted cash, September 30		$199.7			$247.8			$185.3			$236.3			$9.6			$7.7

Operating Activities - The following items contributed to increased (decreased) operating activity cash flows for the nine months ended September 30, 2019 compared to the same period in 2018 (in millions):

	Alliant Energy			IPL			WPL
Higher collections from IPL’s retail electric and gas base rate increases		$84			$84			$—
Changes in amounts refunded to customers related to Federal Tax Reform	35			6			29
Changes in income taxes paid/refunded	6			11			4
Contributions to qualified defined benefit pension plans in 2019	(24		)	(12		)	(12		)
Changes in interest payments	(23		)	(5		)	(5		)
Changes in levels of production fuel	(20		)	(5		)	(15		)
Decreased collections from IPL’s and WPL’s retail customers caused by temperature impacts on electric and gas sales	(15		)	(8		)	(7		)
Timing of intercompany payments and receipts	—			19			1
Other	24			10			19
		$67			$100			$14

Investing Activities - The following items contributed to increased (decreased) investing activity cash flows for the nine months ended September 30, 2019 compared to the same period in 2018 (in millions):

	Alliant Energy			IPL			WPL
Changes in the amount of cash receipts on sold receivables		($81	)		($81	)		$—
Lower (higher) utility construction and acquisition expenditures (a)	76			(61		)	137
Other	(40		)	(13		)	(3		)
		($45	)		($155	)		$134

(a) Largely due to lower WPL expenditures related to the acquisition of a partial interest in the Forward Wind Energy Center in 2018 and lower expenditures for the West Riverside Energy Center, partially offset by higher IPL expenditures related to its expansion of wind generation.

36

Construction and Acquisition Expenditures - Construction and acquisition expenditures for 2019 through 2023 are currently anticipated as follows (in millions). Cost estimates represent Alliant Energy’s, IPL’s and WPL’s portion of construction expenditures and exclude allowance for funds used during construction and capitalized interest, if applicable. Such amounts do not include IPL’s expected $110 million buyout payment in September 2020 related to the DAEC PPA. Such estimates reflect reductions to Alliant Energy’s and WPL’s capital expenditures resulting from purchase options by certain electric cooperatives for a partial ownership interest in the West Riverside Energy Center; however, such estimates do not reflect any potential proceeds if neighboring utilities exercise options for a partial ownership in the West Riverside Energy Center.

	Alliant Energy										IPL										WPL
	2019		2020		2021		2022		2023		2019		2020		2021		2022		2023		2019		2020		2021		2022		2023
Generation:
Renewable projects		$640		$260		$110		$275		$390		$525		$135		$—		$—		$—		$115		$125		$110		$275		$390
West Riverside	80		15		—		—		—		—		—		—		—		—		80		15		—		—		—
Other	105		190		140		170		90		55		90		85		125		50		50		100		55		45		40
Distribution:
Electric systems	450		570		535		525		540		270		320		285		270		310		180		250		250		255		230
Gas systems	95		185		80		130		105		50		50		45		95		65		45		135		35		35		40
Other	150		205		180		235		245		20		30		10		10		15		15		15		10		20		15
		$1,520		$1,425		$1,045		$1,335		$1,370		$920		$625		$425		$500		$440		$485		$640		$460		$630		$715

Financing Activities - The following items contributed to increased (decreased) financing activity cash flows for the nine months ended September 30, 2019 compared to the same period in 2018 (in millions):

	Alliant Energy			IPL			WPL
Lower (higher) payments to retire long-term debt		$350			$100			($250	)
Net changes in the amount of commercial paper and other short-term borrowings outstanding	187			(50		)	(119		)
Higher (lower) net proceeds from issuance of long-term debt	(550		)	100			350
Lower capital contributions from IPL’s and WPL’s parent company, Alliant Energy	—			(130		)	(100		)
Other	(48		)	(21		)	(12		)
		($61	)		($1	)		($131	)

State Regulatory Financing Authorizations - In October 2019, WPL received authorization from the PSCW to issue up to $350 million of long-term debt securities in aggregate in 2020.

Common Stock Issuances and Common Stock Dividends - Refer to Note 5 for discussion of common stock issuances by Alliant Energy in 2019. Refer to “Results of Operations” for discussion of expected issuances of common stock and common stock dividends in 2020.

Short- and Long-term Debt - Refer to Note 6 for discussion of amendments to the single credit facility agreement in March 2019, and IPL’s and WPL’s issuances of long-term debt in 2019. Refer to “Results of Operations” for discussion of expected issuances of long-term debt in 2020.

Off-Balance Sheet Arrangements - A summary of Alliant Energy’s off-balance sheet arrangements is included in the 2018 Form 10-K and has not changed materially from the items reported in the 2018 Form 10-K, except for the items described in Note 3.

Certain Financial Commitments -

Contractual Obligations - A summary of Alliant Energy’s, IPL’s and WPL’s contractual obligations is included in the 2018 Form 10-K and has not changed materially from the items reported in the 2018 Form 10-K, except for the items described in Notes 6, 7 and 14.

37

OTHER MATTERS

Critical Accounting Policies and Estimates - The summary of critical accounting policies and estimates included in the 2018 Form 10-K has not changed materially, except as described below.

Long-Lived Assets -

Regulated Operations -

Assets Subject to Early Retirement - Upon completion of the phased installation of an advanced metering infrastructure program, IPL retired certain analog electric meters in September 2019. IPL’s retail electric rate review settlement, described in Note 2, includes recovery of the remaining net book value of these meters from IPL’s retail customers. However, the settlement does not allow IPL to earn a return on the remaining net book value when final rates are implemented, and as a result, Alliant Energy and IPL recorded a $4 million write-down of regulatory assets in the third quarter of 2019.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

Quantitative and Qualitative Disclosures About Market Risk are reported in the 2018 Form 10-K and have not changed materially.

ITEM 4. CONTROLS AND PROCEDURES

Alliant Energy’s, IPL’s and WPL’s management evaluated, with the participation of each of Alliant Energy’s, IPL’s and WPL’s Chief Executive Officer, Chief Financial Officer and Disclosure Committee, the effectiveness of the design and operation of Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures (as defined in Rule 13a-15(e) of the Securities Exchange Act of 1934) as of September 30, 2019 pursuant to the requirements of the Securities Exchange Act of 1934, as amended. Based on their evaluation, the Chief Executive Officer and the Chief Financial Officer concluded that Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures were effective as of the quarter ended September 30, 2019.

There was no change in Alliant Energy’s, IPL’s and WPL’s internal control over financial reporting that occurred during the quarter ended September 30, 2019 that has materially affected, or is reasonably likely to materially affect, Alliant Energy’s, IPL’s or WPL’s internal control over financial reporting.

PART II. OTHER INFORMATION

ITEM 1A. RISK FACTORS

The risk factors described in Item 1A in the 2018 Form 10-K have not changed materially.

ITEM 2. UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS

A summary of Alliant Energy common stock repurchases for the quarter ended September 30, 2019 was as follows:

	Total Number	Average Price		Total Number of Shares	Maximum Number (or Approximate
	of Shares	Paid Per		Purchased as Part of	Dollar Value) of Shares That May
Period	Purchased (a)	Share		Publicly Announced Plan	Yet Be Purchased Under the Plan (a)
July 1 through July 31	1,895		$50.25	—	N/A
August 1 through August 31	2,803	51.57		—	N/A
September 1 through September 30	165	52.72		—	N/A
	4,863	51.09		—

(a) All shares were purchased on the open market and held in a rabbi trust under the Alliant Energy Deferred Compensation Plan. There is no limit on the number of shares of Alliant Energy common stock that may be held under the Deferred Compensation Plan, which currently does not have an expiration date.

38

ITEM 6. EXHIBITS

The following Exhibits are filed herewith or incorporated herein by reference.

Exhibit Number	Description
4.1	Officer’s Certificate, dated as of September 26, 2019, creating IPL’s 3.50% Senior Debentures due September 30, 2049 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 26, 2019 (File No. 1-4117))
31.1	Certification of the Chief Executive Officer for Alliant Energy
31.2	Certification of the Chief Financial Officer for Alliant Energy
31.3	Certification of the Chief Executive Officer for IPL
31.4	Certification of the Chief Financial Officer for IPL
31.5	Certification of the Chief Executive Officer for WPL
31.6	Certification of the Chief Financial Officer for WPL
32.1	Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for Alliant Energy
32.2	Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for IPL
32.3	Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for WPL
101.INS	Inline XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document
101.SCH	Inline XBRL Taxonomy Extension Schema Document
101.CAL	Inline XBRL Taxonomy Extension Calculation Linkbase Document
101.LAB	Inline XBRL Taxonomy Extension Label Linkbase Document
101.PRE	Inline XBRL Taxonomy Extension Presentation Linkbase Document
101.DEF	Inline XBRL Taxonomy Extension Definition Linkbase Document
104	Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company have each duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized on the 7th day of November 2019.

ALLIANT ENERGY CORPORATION
Registrant
By: /s/ Benjamin M. Bilitz	Chief Accounting Officer and Controller
Benjamin M. Bilitz	(Principal Accounting Officer and Authorized Signatory)

INTERSTATE POWER AND LIGHT COMPANY
Registrant
By: /s/ Benjamin M. Bilitz	Chief Accounting Officer and Controller
Benjamin M. Bilitz	(Principal Accounting Officer and Authorized Signatory)

WISCONSIN POWER AND LIGHT COMPANY
Registrant
By: /s/ Benjamin M. Bilitz	Chief Accounting Officer and Controller
Benjamin M. Bilitz	(Principal Accounting Officer and Authorized Signatory)

39

EX-31.1

Exhibit 31.1

Certification of the Chief Executive Officer for Alliant Energy Corporation

I, John O. Larsen, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Alliant Energy Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 7, 2019

/s/ John O. Larsen

John O. Larsen

Chairman, President and Chief Executive Officer

EX-31.2

Exhibit 31.2

Certification of the Chief Financial Officer for Alliant Energy Corporation

I, Robert J. Durian, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Alliant Energy Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 7, 2019

/s/ Robert J. Durian

Robert J. Durian

Senior Vice President and Chief Financial Officer

EX-31.3

Exhibit 31.3

Certification of the Chief Executive Officer for Interstate Power and Light Company

I, John O. Larsen, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Interstate Power and Light Company;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 7, 2019

/s/ John O. Larsen

John O. Larsen

Chairman and Chief Executive Officer

EX-31.4

Exhibit 31.4

Certification of the Chief Financial Officer for Interstate Power and Light Company

I, Robert J. Durian, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Interstate Power and Light Company;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 7, 2019

/s/ Robert J. Durian

Robert J. Durian

Senior Vice President and Chief Financial Officer

EX-31.5

Exhibit 31.5

Certification of the Chief Executive Officer for Wisconsin Power and Light Company

I, John O. Larsen, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Wisconsin Power and Light Company;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 7, 2019

/s/ John O. Larsen

John O. Larsen

Chairman and Chief Executive Officer

EX-31.6

Exhibit 31.6

Certification of the Chief Financial Officer for Wisconsin Power and Light Company

I, Robert J. Durian, certify that:

1. I have reviewed this quarterly report on Form 10-Q of Wisconsin Power and Light Company;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 7, 2019

/s/ Robert J. Durian

Robert J. Durian

Senior Vice President and Chief Financial Officer

EX-32.1

Exhibit 32.1

Written Statement of the Chief Executive Officer and Chief Financial Officer

Pursuant to 18 U.S.C. §1350

Solely for the purposes of complying with 18 U.S.C. §1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, we, the undersigned Chief Executive Officer and Chief Financial Officer of Alliant Energy Corporation (the “Company”), hereby certify, based on our knowledge, that the Quarterly Report on Form 10-Q of the Company for the quarter ended September 30, 2019 (the “Report”) fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934 and that information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ John O. Larsen

John O. Larsen

Chairman, President and Chief Executive Officer

/s/ Robert J. Durian

Robert J. Durian

Senior Vice President and Chief Financial Officer

November 7, 2019

EX-32.2

Exhibit 32.2

Written Statement of the Chief Executive Officer and Chief Financial Officer

Pursuant to 18 U.S.C. §1350

Solely for the purposes of complying with 18 U.S.C. §1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, we, the undersigned Chief Executive Officer and Chief Financial Officer of Interstate Power and Light Company (the “Company”), hereby certify, based on our knowledge, that the Quarterly Report on Form 10-Q of the Company for the quarter ended September 30, 2019 (the “Report”) fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934 and that information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ John O. Larsen

John O. Larsen

Chairman and Chief Executive Officer

/s/ Robert J. Durian

Robert J. Durian

Senior Vice President and Chief Financial Officer

November 7, 2019

EX-32.3

Exhibit 32.3

Written Statement of the Chief Executive Officer and Chief Financial Officer

Pursuant to 18 U.S.C. §1350

Solely for the purposes of complying with 18 U.S.C. §1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, we, the undersigned Chief Executive Officer and Chief Financial Officer of Wisconsin Power and Light Company (the “Company”), hereby certify, based on our knowledge, that the Quarterly Report on Form 10-Q of the Company for the quarter ended September 30, 2019 (the “Report”) fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934 and that information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ John O. Larsen

John O. Larsen

Chairman and Chief Executive Officer

/s/ Robert J. Durian

Robert J. Durian

Senior Vice President and Chief Financial Officer

November 7, 2019

XML

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2018
Regulatory Matters [Line Items]
Regulatory assets		$ 1,840.0		$ 1,737.3
Regulatory liabilities		1,451.0		1,493.2
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets		1,404.0		1,279.0
Regulatory liabilities		733.6		$ 754.9
2020 Forward-looking Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Interim rate annual increase, amount		90.0
Forecast [Member] | 2020 Forward-looking Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Requested rate annual increase, amount			$ 127.0
Billing credit, period			12 months
Forecast [Member] | 2020 Forward-looking Test Period Retail Gas [Member] | IPL [Member]
Regulatory Matters [Line Items]
Requested rate annual increase, amount			$ 12.0
Tax-related [Member] | 2020 Forward-looking Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Regulatory liabilities		27.0
Revenue Subject to Refund [Member] | 2020 Forward-looking Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Regulatory liabilities		8.0
Analog Electric Meters [Member] | Alliant Energy And IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets		$ 36.0
DAEC PPA [Member]
Regulatory Matters [Line Items]
PPA term amendment		5 years
Recovery period, authorized		5 years
DAEC PPA [Member] | Forecast [Member]
Regulatory Matters [Line Items]
Buyout payment	$ 110.0

XML

Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Electric utility	$ 915.9	$ 861.2	$ 2,350.5	$ 2,296.2
Gas utility	41.5	44.8	322.5	299.0
Other utility	11.2	12.3	33.2	36.2
Non-utility	21.6	10.3	61.4	29.6
Total revenues	990.2	928.6	2,767.6	2,661.0
Operating expenses:
Electric production fuel and purchased power	218.5	227.8	601.7	639.5
Electric transmission service	127.5	129.1	362.9	375.2
Cost of gas sold	9.1	11.3	151.1	150.0
Other operation and maintenance	173.7	148.4	527.2	468.8
Depreciation and amortization	143.8	129.0	423.6	376.4
Taxes other than income taxes	27.4	26.9	84.3	78.1
Total operating expenses	700.0	672.5	2,150.8	2,088.0
Operating income	290.2	256.1	616.8	573.0
Other (income) and deductions:
Interest expense	68.3	63.3	203.8	183.8
Equity income from unconsolidated investments, net	(11.6)	(9.8)	(35.2)	(41.6)
Allowance for funds used during construction	(21.9)	(18.8)	(65.6)	(51.8)
Other	3.7	1.6	11.0	6.0
Total other (income) and deductions	38.5	36.3	114.0	96.4
Income before income taxes	251.7	219.8	502.8	476.6
Income tax expense (benefit)	23.1	11.7	49.4	42.1
Net income	228.6	208.1	453.4	434.5
Preferred dividend requirements of Interstate Power and Light Company	2.6	2.6	7.7	7.7
Net income attributable to common shareowners	$ 226.0	$ 205.5	$ 445.7	$ 426.8
Weighted average number of common shares outstanding (basic) (in shares)	239.1	235.2	237.7	232.9
Weighted average number of common shares outstanding (diluted) (in shares)	239.9	235.2	238.2	232.9
Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic) (in dollars per share)	$ 0.95	$ 0.87	$ 1.88	$ 1.83
Earnings per weighted average common share attributable to Alliant Energy common shareowners (diluted) (in dollars per share)	$ 0.94	$ 0.87	$ 1.87	$ 1.83
IPL [Member]
Revenues:
Electric utility	$ 560.9	$ 509.2	$ 1,373.0	$ 1,337.0
Gas utility	24.8	26.7	187.8	177.0
Other utility	10.8	11.7	32.0	34.2
Total revenues	596.5	547.6	1,592.8	1,548.2
Operating expenses:
Electric production fuel and purchased power	126.8	122.5	339.0	354.0
Electric transmission service	91.8	92.8	256.9	268.0
Cost of gas sold	5.9	6.4	80.0	83.8
Other operation and maintenance	100.2	94.6	305.6	297.1
Depreciation and amortization	83.7	73.9	243.4	209.2
Taxes other than income taxes	14.6	14.3	46.4	39.7
Total operating expenses	423.0	404.5	1,271.3	1,251.8
Operating income	173.5	143.1	321.5	296.4
Other (income) and deductions:
Interest expense	31.7	30.4	92.6	90.6
Allowance for funds used during construction	(10.8)	(11.0)	(34.5)	(28.3)
Other	2.0	0.5	5.4	2.0
Total other (income) and deductions	22.9	19.9	63.5	64.3
Income before income taxes	150.6	123.2	258.0	232.1
Income tax expense (benefit)	6.9	(5.9)	10.9	(0.5)
Net income	143.7	129.1	247.1	232.6
Preferred dividend requirements of Interstate Power and Light Company	2.6	2.6	7.7	7.7
Net income attributable to common shareowners	141.1	126.5	239.4	224.9
WPL [Member]
Revenues:
Electric utility	355.0	352.0	977.5	959.2
Gas utility	16.7	18.1	134.7	122.0
Other utility	0.4	0.6	1.2	2.0
Total revenues	372.1	370.7	1,113.4	1,083.2
Operating expenses:
Electric production fuel and purchased power	91.7	105.3	262.7	285.5
Electric transmission service	35.7	36.3	106.0	107.2
Cost of gas sold	3.2	4.9	71.1	66.2
Other operation and maintenance	62.3	54.2	188.2	172.8
Depreciation and amortization	58.9	54.1	176.6	164.2
Taxes other than income taxes	12.0	11.7	35.4	35.7
Total operating expenses	263.8	266.5	840.0	831.6
Operating income	108.3	104.2	273.4	251.6
Other (income) and deductions:
Interest expense	25.4	24.2	77.3	73.5
Allowance for funds used during construction	(11.1)	(7.8)	(31.1)	(23.5)
Other	1.4	1.3	4.6	3.4
Total other (income) and deductions	15.7	17.7	50.8	53.4
Income before income taxes	92.6	86.5	222.6	198.2
Income tax expense (benefit)	17.1	10.2	39.4	28.1
Net income			183.2	170.1
Net income attributable to common shareowners	$ 75.5	$ 76.3	$ 183.2	$ 170.1

XML

Commitments And Contingencies (Tables)

9 Months Ended

Sep. 30, 2019

Commitments and Contingencies [Line Items]

Other Purchase Commitments

At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c)

Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

MGP Site Estimated Future Costs And Recorded Liabilities

At September 30, 2019, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At September 30, 2019, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$14	-	$31		$12	-	$25
Current and non-current environmental liabilities	19				16

IPL [Member]

Commitments and Contingencies [Line Items]

Other Purchase Commitments

At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c)

Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

MGP Site Estimated Future Costs And Recorded Liabilities

At September 30, 2019, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At September 30, 2019, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$14	-	$31		$12	-	$25
Current and non-current environmental liabilities	19				16

WPL [Member]

Commitments and Contingencies [Line Items]

Other Purchase Commitments

At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c)

Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

XML

Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2019

Defined Benefit Plan Disclosure [Line Items]

Defined Benefit Pension And Other Postretirement Benefits Plans

The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

Recognized Compensation Expense And Income Tax Benefits

A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

IPL [Member]

Defined Benefit Plan Disclosure [Line Items]

Defined Benefit Pension And Other Postretirement Benefits Plans

The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

Recognized Compensation Expense And Income Tax Benefits

A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

WPL [Member]

Defined Benefit Plan Disclosure [Line Items]

Defined Benefit Pension And Other Postretirement Benefits Plans

The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

Recognized Compensation Expense And Income Tax Benefits

A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

XML

Summary Of Significant Accounting Policies

9 Months Ended

Sep. 30, 2019

Summary Of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

NOTE 1(b) Cash and Cash Equivalents - At September 30, 2019, Alliant Energy’s and IPL’s cash and cash equivalents included $174.4 million and $173.7 million of money market fund investments, with interest rates of 2.0% and 2.0%, respectively.

NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

NOTE 1(d) New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

IPL [Member]

Summary Of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

NOTE 1(b) Cash and Cash Equivalents - At September 30, 2019, Alliant Energy’s and IPL’s cash and cash equivalents included $174.4 million and $173.7 million of money market fund investments, with interest rates of 2.0% and 2.0%, respectively.

NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

NOTE 1(d) New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

WPL [Member]

Summary Of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

NOTE 1(b) Cash and Cash Equivalents - At September 30, 2019, Alliant Energy’s and IPL’s cash and cash equivalents included $174.4 million and $173.7 million of money market fund investments, with interest rates of 2.0% and 2.0%, respectively.

NOTE 1(c) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

NOTE 1(d) New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

XML

Leases

9 Months Ended

Sep. 30, 2019

Leases [Line Items]

Operating Leases

LEASES

Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions):

	September 30, 2019
Property, plant and equipment, net		$34
Other current liabilities		$8
Finance lease obligations - Sheboygan Falls Energy Facility	54
Total finance lease liabilities		$62
Remaining lease term	6 years
Discount rate	11		%
	Three Months Ended			Nine Months Ended
	September 30, 2019			September 30, 2019
Depreciation expense		$1			$4
Interest expense	1			5
Total finance lease expense		$2			$9

Expected Maturities - As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

IPL [Member]

Leases [Line Items]

Operating Leases

LEASES

Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions):

	September 30, 2019
Property, plant and equipment, net		$34
Other current liabilities		$8
Finance lease obligations - Sheboygan Falls Energy Facility	54
Total finance lease liabilities		$62
Remaining lease term	6 years
Discount rate	11		%
	Three Months Ended			Nine Months Ended
	September 30, 2019			September 30, 2019
Depreciation expense		$1			$4
Interest expense	1			5
Total finance lease expense		$2			$9

Expected Maturities - As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

WPL [Member]

Leases [Line Items]

Operating Leases

LEASES

Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions):

	September 30, 2019
Property, plant and equipment, net		$34
Other current liabilities		$8
Finance lease obligations - Sheboygan Falls Energy Facility	54
Total finance lease liabilities		$62
Remaining lease term	6 years
Discount rate	11		%
	Three Months Ended			Nine Months Ended
	September 30, 2019			September 30, 2019
Depreciation expense		$1			$4
Interest expense	1			5
Total finance lease expense		$2			$9

Expected Maturities - As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

Finance Leases

LEASES

Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Finance Lease - WPL’s finance lease is an agreement for WPL to lease the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. WPL’s retail and wholesale rates include recovery of the Sheboygan Falls Energy Facility lease payments. WPL’s finance lease details are as follows (dollars in millions):

	September 30, 2019
Property, plant and equipment, net		$34
Other current liabilities		$8
Finance lease obligations - Sheboygan Falls Energy Facility	54
Total finance lease liabilities		$62
Remaining lease term	6 years
Discount rate	11		%
	Three Months Ended			Nine Months Ended
	September 30, 2019			September 30, 2019
Depreciation expense		$1			$4
Interest expense	1			5
Total finance lease expense		$2			$9

Expected Maturities - As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Prior period amounts have not been restated to reflect the adoption of the new lease accounting standard and continue to be reported under the accounting standards in effect for those periods. As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

XML

Asset Retirement Obligations

9 Months Ended

Sep. 30, 2019

Asset Retirement Obligations [Line Items]

Asset Retirement Obligations

ASSET RETIREMENT OBLIGATIONS

A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2019 is as follows (in millions):

	Alliant Energy			IPL
Balance, January 1		$177.5			$118.3
Revisions in estimated cash flows	(5.8		)	(7.0		)
Liabilities settled	(5.9		)	(5.6		)
Liabilities incurred (a)	26.2			26.2
Accretion expense	5.3			3.5
Balance, September 30		$197.3			$135.4

(a)

During the nine months ended September 30, 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

IPL [Member]

Asset Retirement Obligations [Line Items]

Asset Retirement Obligations

ASSET RETIREMENT OBLIGATIONS

A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2019 is as follows (in millions):

	Alliant Energy			IPL
Balance, January 1		$177.5			$118.3
Revisions in estimated cash flows	(5.8		)	(7.0		)
Liabilities settled	(5.9		)	(5.6		)
Liabilities incurred (a)	26.2			26.2
Accretion expense	5.3			3.5
Balance, September 30		$197.3			$135.4

(a)

During the nine months ended September 30, 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

XML

Related Parties (Net Intercompany Payables) (Details) - Subsidiary of Common Parent [Member] - Corporate Services [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 108	$ 95
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 75	$ 71

XML

Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	$ 19
IPL [Member]
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	16
Minimum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	14
Minimum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	12
Maximum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	31
Maximum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	$ 25

XML

Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			$ 4,585.7
Beginning balance	$ 4,899.6	$ 4,550.7	4,785.7	$ 4,382.2
Net income attributable to common shareowners	226.0	205.5	445.7	426.8
Common stock dividends	(84.7)	(78.5)	(252.5)	(233.3)
Equity forward settlements, At-the-market offering program and Shareowner Direct Plan issuances	124.8	91.2	185.4	191.3
Equity-based compensation plans and other	3.5	1.8	5.6	3.1
Other comprehensive income (loss), net of tax		(0.3)	(0.7)	0.3
Ending balance	4,969.2		4,969.2
Ending balance	$ 5,169.2	$ 4,770.4	$ 5,169.2	$ 4,770.4
Common stock dividends (in dollars per share)	$ 0.355	$ 0.335	$ 1.065	$ 1.005
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 2.4	$ 2.3	$ 2.4	$ 2.3
Equity forward settlements, At-the-market offering program and Shareowner Direct Plan issuances		0.1		0.1
Ending balance	2.4	2.4	2.4	2.4
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,108.4	1,947.2	2,045.5	1,845.5
Equity forward settlements, At-the-market offering program and Shareowner Direct Plan issuances	124.8	91.1	185.4	191.2
Equity-based compensation plans and other	3.7	(0.1)	6.0	1.5
Ending balance	2,236.9	2,038.2	2,236.9	2,038.2
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,597.8	2,412.5	2,545.9	2,346.0
Net income attributable to common shareowners	226.0	205.5	445.7	426.8
Common stock dividends	(84.7)	(78.5)	(252.5)	(233.3)
Ending balance	2,739.1	2,539.5	2,739.1	2,539.5
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1.0	0.1	1.7	(0.5)
Other comprehensive income (loss), net of tax		(0.3)	(0.7)	0.3
Ending balance	1.0	(0.2)	1.0	(0.2)
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(10.0)	(11.4)	(9.8)	(11.1)
Equity-based compensation plans and other	(0.2)	1.9	(0.4)	1.6
Ending balance	(10.2)	(9.5)	(10.2)	(9.5)
Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	200.0	200.0	200.0	200.0
Ending balance	200.0	200.0	200.0	200.0
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,030.7
Beginning balance	3,345.1	2,854.1	3,230.7	2,709.7
Net income attributable to common shareowners	141.1	126.5	239.4	224.9
Common stock dividends	(42.1)	(41.9)	(126.0)	(125.9)
Capital contributions from parent		100.0	100.0	230.0
Other comprehensive income (loss), net of tax	0.0	0.0	0.0	0.0
Ending balance	3,244.1		3,244.1
Ending balance	3,444.1	3,038.7	3,444.1	3,038.7
IPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	33.4	33.4	33.4	33.4
Ending balance	33.4	33.4	33.4	33.4
IPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,322.8	1,927.8	2,222.8	1,797.8
Capital contributions from parent		100.0	100.0	230.0
Ending balance	2,322.8	2,027.8	2,322.8	2,027.8
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	788.9	692.9	774.5	678.5
Net income attributable to common shareowners	141.1	126.5	239.4	224.9
Common stock dividends	(42.1)	(41.9)	(126.0)	(125.9)
Ending balance	887.9	777.5	887.9	777.5
IPL [Member] | Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	200.0	200.0	200.0	200.0
Ending balance	200.0	200.0	200.0	200.0
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			2,149.5
Beginning balance	2,185.2	2,055.2	2,149.5	1,881.5
Net income attributable to common shareowners	75.5	76.3	183.2	170.1
Common stock dividends	(35.9)	(34.9)	(107.9)	(105.0)
Capital contributions from parent	100.0	50.0	100.0	200.0
Other comprehensive income (loss), net of tax	0.0	0.0	0.0	0.0
Ending balance	2,324.8		2,324.8
Ending balance	2,324.8	2,146.6	2,324.8	2,146.6
WPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	66.2	66.2	66.2	66.2
Ending balance	66.2	66.2	66.2	66.2
WPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,309.0	1,259.0	1,309.0	1,109.0
Capital contributions from parent	100.0	50.0	100.0	200.0
Ending balance	1,409.0	1,309.0	1,409.0	1,309.0
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	810.0	730.0	774.3	706.3
Net income attributable to common shareowners	75.5	76.3	183.2	170.1
Common stock dividends	(35.9)	(34.9)	(107.9)	(105.0)
Ending balance	$ 849.6	$ 771.4	$ 849.6	$ 771.4

XML

Leases (Narrative) (Details)	12 Months Ended
	Dec. 31, 2005 lease_renewal_period_option
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance leases, renewal options (in number of renewal periods)	2

XML

Leases (Future Minimum Operating and Capital Lease Payments) (Details) $ in Millions	Dec. 31, 2018 USD ($)
Leases [Line Items]
Operating Leases, 2019	$ 5
Operating Leases, 2020	5
Operating Leases, 2021	3
Operating Leases, 2022	3
Operating Leases, 2023	2
Operating Leases, Thereafter	12
Operating Leases, Total	30
IPL [Member]
Leases [Line Items]
Operating Leases, 2019	3
Operating Leases, 2020	2
Operating Leases, 2021	2
Operating Leases, 2022	2
Operating Leases, 2023	2
Operating Leases, Thereafter	12
Operating Leases, Total	23
WPL [Member]
Leases [Line Items]
Operating Leases, 2019	2
Operating Leases, 2020	3
Operating Leases, 2021	1
Operating Leases, 2022	0
Operating Leases, 2023	0
Operating Leases, Thereafter	0
Operating Leases, Total	6
WPL [Member] | Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Capital Leases, 2019	15
Capital Leases, 2020	15
Capital Leases, 2021	15
Capital Leases, 2022	15
Capital Leases, 2023	15
Capital Leases, Thereafter	19
Capital Leases, Total	94
Capital Leases, Less: amount representing interest	26
Capital Leases, Present value of minimum capital lease payments	$ 68

XML

Benefit Plans (Narrative) (Details) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost | $	$ 7.2
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	1 year
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	2 years
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost | $	$ 4.0
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost | $	$ 2.9
Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Performance period	3 years
Granted (in shares/awards)	91,816
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 47.23
Shares included in diluted earnings per share (in shares)	122,720
Performance Shares [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0.00%
Performance Shares [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200.00%
Performance Restricted Stock Unit [Member]
Defined Benefit Plan Disclosure [Line Items]
Performance period	3 years
Granted (in shares/awards)	91,816
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 46.10
Instrument valuation based on shares of common stock, number of shares	1
Performance Restricted Stock Unit [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0.00%
Performance Restricted Stock Unit [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200.00%
Restricted Stock Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Performance period	3 years
Granted (in shares/awards)	105,348
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 45.98
Instrument valuation based on shares of common stock, number of shares	1

XML

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] gal in Thousands, T in Thousands, MWh in Thousands, Dekatherms in Thousands	9 Months Ended
	Sep. 30, 2019 Dekatherms MWh T gal
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	18,141
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	8,630
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	9,511
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	184,007
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	101,579
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	82,428
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	7,620
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	3,311
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	4,309
Diesel Fuel (Gallons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	5,796
Diesel Fuel (Gallons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	0
Diesel Fuel (Gallons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	5,796

XML

Common Equity (Common Share Activity) (Details)	9 Months Ended
	Sep. 30, 2019 shares
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1, 2019 (in shares)	236,063,279
Shareowner Direct Plan (in shares)	390,630
Equity-based compensation plans (in shares)	101,478
Other (in shares)	(2,738)
Shares outstanding, September 30, 2019 (in shares)	240,342,949
Equity Forward Agreements [Member]
Common Stock Oustanding [Roll Forward]
Equity forward agreements (in shares)	3,790,300

XML

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Receivables [Line Items]
Collections	$ 592.2	$ 549.5	$ 1,635.7	$ 1,550.2
Write-offs, net of recoveries	$ 3.2	$ 4.9	$ 11.3	$ 12.9

XML

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,451.0	$ 1,493.2
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	851.4	890.6
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	390.9	401.2
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	89.8	104.0
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	29.1	16.8
WPL's earnings sharing mechanism [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	21.8	25.4
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	20.8	18.5
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	47.2	36.7
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	733.6	754.9
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	365.0	390.1
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	261.0	273.3
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	48.0	47.7
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	16.7	11.9
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	16.9	10.2
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	26.0	21.7
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	717.4	738.3
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	486.4	500.5
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	129.9	127.9
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	41.8	56.3
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	12.4	4.9
WPL [Member] | WPL's earnings sharing mechanism [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	21.8	25.4
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	3.9	8.3
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 21.2	$ 15.0

XML

Segments Of Business

9 Months Ended

Sep. 30, 2019

Segment Reporting Information [Line Items]

Segments Of Business

SEGMENTS OF BUSINESS

Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations.

										ATC Holdings,		Alliant
	Utility									Non-Utility,		Energy
	Electric		Gas			Other		Total		Parent and Other		Consolidated
	(in millions)
Three Months Ended September 30, 2019
Revenues		$915.9		$41.5			$11.2		$968.6		$21.6		$990.2
Operating income (loss)	283.7		(4.7		)	2.8		281.8		8.4		290.2
Net income attributable to Alliant Energy common shareowners								216.6		9.4		226.0
Three Months Ended September 30, 2018
Revenues		$861.2		$44.8			$12.3		$918.3		$10.3		$928.6
Operating income (loss)	248.7		(2.0		)	0.6		247.3		8.8		256.1
Net income attributable to Alliant Energy common shareowners								202.8		2.7		205.5

									ATC Holdings,		Alliant
	Utility								Non-Utility,		Energy
	Electric		Gas		Other		Total		Parent and Other		Consolidated
	(in millions)
Nine Months Ended September 30, 2019
Revenues		$2,350.5		$322.5		$33.2		$2,706.2		$61.4		$2,767.6
Operating income	543.0		47.7		4.2		594.9		21.9		616.8
Net income attributable to Alliant Energy common shareowners							422.6		23.1		445.7
Nine Months Ended September 30, 2018
Revenues		$2,296.2		$299.0		$36.2		$2,631.4		$29.6		$2,661.0
Operating income	510.2		34.9		2.9		548.0		25.0		573.0
Net income attributable to Alliant Energy common shareowners							395.0		31.8		426.8

IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations.

	Electric		Gas			Other		Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$560.9		$24.8			$10.8		$596.5
Operating income (loss)	175.1		(4.2		)	2.6		173.5
Earnings available for common stock								141.1
Three Months Ended September 30, 2018
Revenues		$509.2		$26.7			$11.7		$547.6
Operating income (loss)	144.7		(3.1		)	1.5		143.1
Earnings available for common stock								126.5
Nine Months Ended September 30, 2019
Revenues		$1,373.0		$187.8			$32.0		$1,592.8
Operating income	290.8		26.3			4.4		321.5
Earnings available for common stock								239.4
Nine Months Ended September 30, 2018
Revenues		$1,337.0		$177.0			$34.2		$1,548.2
Operating income	275.7		16.3			4.4		296.4
Earnings available for common stock								224.9

WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations.

	Electric		Gas			Other			Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$355.0		$16.7			$0.4			$372.1
Operating income (loss)	108.6		(0.5		)	0.2			108.3
Earnings available for common stock									75.5
Three Months Ended September 30, 2018
Revenues		$352.0		$18.1			$0.6			$370.7
Operating income (loss)	104.0		1.1			(0.9		)	104.2
Earnings available for common stock									76.3
Nine Months Ended September 30, 2019
Revenues		$977.5		$134.7			$1.2			$1,113.4
Operating income (loss)	252.2		21.4			(0.2		)	273.4
Earnings available for common stock									183.2
Nine Months Ended September 30, 2018
Revenues		$959.2		$122.0			$2.0			$1,083.2
Operating income (loss)	234.5		18.6			(1.5		)	251.6
Earnings available for common stock									170.1

IPL [Member]

Segment Reporting Information [Line Items]

Segments Of Business

SEGMENTS OF BUSINESS

Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations.

										ATC Holdings,		Alliant
	Utility									Non-Utility,		Energy
	Electric		Gas			Other		Total		Parent and Other		Consolidated
	(in millions)
Three Months Ended September 30, 2019
Revenues		$915.9		$41.5			$11.2		$968.6		$21.6		$990.2
Operating income (loss)	283.7		(4.7		)	2.8		281.8		8.4		290.2
Net income attributable to Alliant Energy common shareowners								216.6		9.4		226.0
Three Months Ended September 30, 2018
Revenues		$861.2		$44.8			$12.3		$918.3		$10.3		$928.6
Operating income (loss)	248.7		(2.0		)	0.6		247.3		8.8		256.1
Net income attributable to Alliant Energy common shareowners								202.8		2.7		205.5

									ATC Holdings,		Alliant
	Utility								Non-Utility,		Energy
	Electric		Gas		Other		Total		Parent and Other		Consolidated
	(in millions)
Nine Months Ended September 30, 2019
Revenues		$2,350.5		$322.5		$33.2		$2,706.2		$61.4		$2,767.6
Operating income	543.0		47.7		4.2		594.9		21.9		616.8
Net income attributable to Alliant Energy common shareowners							422.6		23.1		445.7
Nine Months Ended September 30, 2018
Revenues		$2,296.2		$299.0		$36.2		$2,631.4		$29.6		$2,661.0
Operating income	510.2		34.9		2.9		548.0		25.0		573.0
Net income attributable to Alliant Energy common shareowners							395.0		31.8		426.8

IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations.

	Electric		Gas			Other		Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$560.9		$24.8			$10.8		$596.5
Operating income (loss)	175.1		(4.2		)	2.6		173.5
Earnings available for common stock								141.1
Three Months Ended September 30, 2018
Revenues		$509.2		$26.7			$11.7		$547.6
Operating income (loss)	144.7		(3.1		)	1.5		143.1
Earnings available for common stock								126.5
Nine Months Ended September 30, 2019
Revenues		$1,373.0		$187.8			$32.0		$1,592.8
Operating income	290.8		26.3			4.4		321.5
Earnings available for common stock								239.4
Nine Months Ended September 30, 2018
Revenues		$1,337.0		$177.0			$34.2		$1,548.2
Operating income	275.7		16.3			4.4		296.4
Earnings available for common stock								224.9

WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations.

	Electric		Gas			Other			Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$355.0		$16.7			$0.4			$372.1
Operating income (loss)	108.6		(0.5		)	0.2			108.3
Earnings available for common stock									75.5
Three Months Ended September 30, 2018
Revenues		$352.0		$18.1			$0.6			$370.7
Operating income (loss)	104.0		1.1			(0.9		)	104.2
Earnings available for common stock									76.3
Nine Months Ended September 30, 2019
Revenues		$977.5		$134.7			$1.2			$1,113.4
Operating income (loss)	252.2		21.4			(0.2		)	273.4
Earnings available for common stock									183.2
Nine Months Ended September 30, 2018
Revenues		$959.2		$122.0			$2.0			$1,083.2
Operating income (loss)	234.5		18.6			(1.5		)	251.6
Earnings available for common stock									170.1

WPL [Member]

Segment Reporting Information [Line Items]

Segments Of Business

SEGMENTS OF BUSINESS

Alliant Energy - Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations.

										ATC Holdings,		Alliant
	Utility									Non-Utility,		Energy
	Electric		Gas			Other		Total		Parent and Other		Consolidated
	(in millions)
Three Months Ended September 30, 2019
Revenues		$915.9		$41.5			$11.2		$968.6		$21.6		$990.2
Operating income (loss)	283.7		(4.7		)	2.8		281.8		8.4		290.2
Net income attributable to Alliant Energy common shareowners								216.6		9.4		226.0
Three Months Ended September 30, 2018
Revenues		$861.2		$44.8			$12.3		$918.3		$10.3		$928.6
Operating income (loss)	248.7		(2.0		)	0.6		247.3		8.8		256.1
Net income attributable to Alliant Energy common shareowners								202.8		2.7		205.5

									ATC Holdings,		Alliant
	Utility								Non-Utility,		Energy
	Electric		Gas		Other		Total		Parent and Other		Consolidated
	(in millions)
Nine Months Ended September 30, 2019
Revenues		$2,350.5		$322.5		$33.2		$2,706.2		$61.4		$2,767.6
Operating income	543.0		47.7		4.2		594.9		21.9		616.8
Net income attributable to Alliant Energy common shareowners							422.6		23.1		445.7
Nine Months Ended September 30, 2018
Revenues		$2,296.2		$299.0		$36.2		$2,631.4		$29.6		$2,661.0
Operating income	510.2		34.9		2.9		548.0		25.0		573.0
Net income attributable to Alliant Energy common shareowners							395.0		31.8		426.8

IPL - Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations.

	Electric		Gas			Other		Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$560.9		$24.8			$10.8		$596.5
Operating income (loss)	175.1		(4.2		)	2.6		173.5
Earnings available for common stock								141.1
Three Months Ended September 30, 2018
Revenues		$509.2		$26.7			$11.7		$547.6
Operating income (loss)	144.7		(3.1		)	1.5		143.1
Earnings available for common stock								126.5
Nine Months Ended September 30, 2019
Revenues		$1,373.0		$187.8			$32.0		$1,592.8
Operating income	290.8		26.3			4.4		321.5
Earnings available for common stock								239.4
Nine Months Ended September 30, 2018
Revenues		$1,337.0		$177.0			$34.2		$1,548.2
Operating income	275.7		16.3			4.4		296.4
Earnings available for common stock								224.9

WPL - Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations.

	Electric		Gas			Other			Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$355.0		$16.7			$0.4			$372.1
Operating income (loss)	108.6		(0.5		)	0.2			108.3
Earnings available for common stock									75.5
Three Months Ended September 30, 2018
Revenues		$352.0		$18.1			$0.6			$370.7
Operating income (loss)	104.0		1.1			(0.9		)	104.2
Earnings available for common stock									76.3
Nine Months Ended September 30, 2019
Revenues		$977.5		$134.7			$1.2			$1,113.4
Operating income (loss)	252.2		21.4			(0.2		)	273.4
Earnings available for common stock									183.2
Nine Months Ended September 30, 2018
Revenues		$959.2		$122.0			$2.0			$1,083.2
Operating income (loss)	234.5		18.6			(1.5		)	251.6
Earnings available for common stock									170.1

XML

Receivables (Tables)

9 Months Ended

Sep. 30, 2019

Receivables [Line Items]

Maximum And Average Outstanding Cash Proceeds

IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Maximum outstanding aggregate cash proceeds		$103.0		$110.0		$108.0		$116.0
Average outstanding aggregate cash proceeds	45.4		36.4		42.9		49.8

Receivables Sold Under The Receivables Agreement

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

	September 30, 2019		December 31, 2018
Customer accounts receivable		$154.2		$140.1
Unbilled utility revenues	92.1		97.1
Other receivables	0.4		0.1
Receivables sold to third party	246.7		237.3
Less: cash proceeds	1.0		108.0
Deferred proceeds	245.7		129.3
Less: allowance for doubtful accounts	8.7		9.9
Fair value of deferred proceeds		$237.0		$119.4

Additional Attributes Of Receivables Sold Under The Receivables Agreement

Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Collections		$592.2		$549.5		$1,635.7		$1,550.2
Write-offs, net of recoveries	3.2		4.9		11.3		12.9

IPL [Member]

Receivables [Line Items]

Maximum And Average Outstanding Cash Proceeds

IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Maximum outstanding aggregate cash proceeds		$103.0		$110.0		$108.0		$116.0
Average outstanding aggregate cash proceeds	45.4		36.4		42.9		49.8

Receivables Sold Under The Receivables Agreement

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

	September 30, 2019		December 31, 2018
Customer accounts receivable		$154.2		$140.1
Unbilled utility revenues	92.1		97.1
Other receivables	0.4		0.1
Receivables sold to third party	246.7		237.3
Less: cash proceeds	1.0		108.0
Deferred proceeds	245.7		129.3
Less: allowance for doubtful accounts	8.7		9.9
Fair value of deferred proceeds		$237.0		$119.4

Additional Attributes Of Receivables Sold Under The Receivables Agreement

Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Collections		$592.2		$549.5		$1,635.7		$1,550.2
Write-offs, net of recoveries	3.2		4.9		11.3		12.9

XML

Leases (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Line Items]

Schedule of Lease Details

Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Schedule of Operating Lease Liability Maturities

As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Schedule of Future Minimum Payments for Operating Leases

As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

IPL [Member]

Leases [Line Items]

Schedule of Lease Details

Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Schedule of Operating Lease Liability Maturities

As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Schedule of Future Minimum Payments for Operating Leases

As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

WPL [Member]

Leases [Line Items]

Schedule of Lease Details

WPL’s finance lease details are as follows (dollars in millions):

	September 30, 2019
Property, plant and equipment, net		$34
Other current liabilities		$8
Finance lease obligations - Sheboygan Falls Energy Facility	54
Total finance lease liabilities		$62
Remaining lease term	6 years
Discount rate	11		%
	Three Months Ended			Nine Months Ended
	September 30, 2019			September 30, 2019
Depreciation expense		$1			$4
Interest expense	1			5
Total finance lease expense		$2			$9

Operating lease details are as follows (dollars in millions):

	September 30, 2019
	Alliant Energy			IPL			WPL
Property, plant and equipment, net		$17			$10			$7
Other current liabilities		$2			$1			$1
Other liabilities	15			9			6
Total operating lease liabilities		$17			$10			$7
Weighted average remaining lease term	11 years			12 years			10 years
Weighted average discount rate	4		%	4		%	4		%
	Three Months Ended									Nine Months Ended
	September 30, 2019									September 30, 2019
	Alliant Energy			IPL			WPL			Alliant Energy		IPL		WPL
Operating lease cost		$1			$1			$—			$2		$1		$—

Schedule of Operating Lease Liability Maturities

As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Schedule of Finance Lease Liability Maturities

As of September 30, 2019, expected maturities of lease liabilities were as follows (in millions):

	Remainder of 2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum lease payments
Operating Leases:
Alliant Energy		$—		$2		$2		$2		$2		$13		$21		$4		$17
IPL	—		1		1		1		1		9		13		3		10
WPL	—		1		1		1		1		4		8		1		7
WPL’s Finance Lease:
Sheboygan Falls Energy Facility	4		15		15		15		15		20		84		22		62

Schedule of Future Minimum Payments for Operating Leases

As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

Schedule of Future Minimum Payments for Capital Leases

As of December 31, 2018, future minimum operating (excluding contingent rentals) and capital lease payments were as follows (in millions):

	2019		2020		2021		2022		2023		Thereafter		Total		Less: amount representing interest		Present value of minimum capital lease payments
Operating Leases:
Alliant Energy		$5		$5		$3		$3		$2		$12		$30
IPL	3		2		2		2		2		12		23
WPL	2		3		1		—		—		—		6
WPL’s Capital Lease:
Sheboygan Falls Energy Facility		$15		$15		$15		$15		$15		$19		$94		$26		$68

XML

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2.5	$ 3.1	$ 7.3	$ 9.1
Interest cost	12.5	11.7	37.4	35.1
Expected return on plan assets	(15.1)	(17.4)	(45.1)	(52.3)
Amortization of prior service credit	(0.2)	(0.2)	(0.5)	(0.5)
Amortization of actuarial loss	9.1	8.8	27.3	26.4
Total	8.8	6.0	26.4	17.8
OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.8	1.0	2.5	3.1
Interest cost	2.2	2.0	6.4	5.8
Expected return on plan assets	(1.2)	(1.5)	(3.7)	(4.5)
Amortization of prior service credit	(0.1)	0.0	(0.2)	(0.1)
Amortization of actuarial loss	0.8	0.8	2.4	2.5
Total	2.5	2.3	7.4	6.8
IPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.6	1.8	4.6	5.5
Interest cost	5.6	5.3	17.0	16.0
Expected return on plan assets	(7.0)	(8.1)	(21.1)	(24.4)
Amortization of prior service credit	(0.1)	0.0	(0.2)	(0.1)
Amortization of actuarial loss	3.9	3.7	11.8	11.2
Total	4.0	2.7	12.1	8.2
IPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.3	0.4	1.0	1.3
Interest cost	0.8	0.7	2.5	2.3
Expected return on plan assets	(0.9)	(1.1)	(2.7)	(3.3)
Amortization of prior service credit	0.0	0.0	0.0	0.0
Amortization of actuarial loss	0.4	0.4	1.1	1.0
Total	0.6	0.4	1.9	1.3
WPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.9	1.1	2.6	3.3
Interest cost	5.3	5.0	16.1	15.1
Expected return on plan assets	(6.5)	(7.6)	(19.6)	(22.8)
Amortization of prior service credit	0.0	0.0	(0.1)	(0.1)
Amortization of actuarial loss	4.4	4.3	13.2	12.9
Total	4.1	2.8	12.2	8.4
WPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.3	0.4	0.9	1.2
Interest cost	0.9	0.8	2.6	2.3
Expected return on plan assets	(0.2)	(0.2)	(0.5)	(0.5)
Amortization of prior service credit	0.0	0.0	(0.1)	(0.1)
Amortization of actuarial loss	0.4	0.5	1.2	1.5
Total	$ 1.4	$ 1.5	$ 4.1	$ 4.4

XML

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 18.6	$ 24.6
Non-current derivative assets	11.7	3.7
Current derivative liabilities	13.4	5.6
Non-current derivative liabilities	18.4	17.7
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	12.8	16.1
Non-current derivative assets	10.5	1.6
Current derivative liabilities	5.6	3.1
Non-current derivative liabilities	7.8	8.1
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	5.8	8.5
Non-current derivative assets	1.2	2.1
Current derivative liabilities	7.8	2.5
Non-current derivative liabilities	$ 10.6	$ 9.6

XML

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Receivables [Line Items]
Fair value of deferred proceeds	$ 237.0	$ 119.4
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	237.0	119.4
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	154.2	140.1
Unbilled utility revenues	92.1	97.1
Other receivables	0.4	0.1
Receivables sold to third party	246.7	237.3
Less: cash proceeds	1.0	108.0
Deferred proceeds	245.7	129.3
Less: allowance for doubtful accounts	8.7	9.9
Fair value of deferred proceeds	$ 237.0	$ 119.4

XML

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Regulatory assets	$ 1,840.0	$ 1,737.3
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	825.2	820.6
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	513.1	542.3
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	138.7	111.6
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	110.7	110.8
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	107.7	0.0
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	34.0	28.0
Emission allowances [Member]
Regulatory Assets [Line Items]
Regulatory assets	21.7	23.6
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	88.9	100.4
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,404.0	1,279.0
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	787.2	783.1
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	260.0	274.0
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	90.1	55.4
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	75.2	76.3
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	107.7	0.0
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	15.0	15.1
IPL [Member] | Emission allowances [Member]
Regulatory Assets [Line Items]
Regulatory assets	21.7	23.6
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	47.1	51.5
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	436.0	458.3
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	38.0	37.5
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	253.1	268.3
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	48.6	56.2
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	35.5	34.5
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	19.0	12.9
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 41.8	$ 48.9

XML

Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Common Equity [Line Items]
Proceeds from issuance of common stock, net	$ 124.8	$ 91.2	$ 185.4	$ 191.3
Comprehensive income (loss)		(0.3)	(0.7)	0.3
IPL [Member]
Common Equity [Line Items]
Comprehensive income (loss)	0.0	0.0	0.0	0.0
WPL [Member]
Common Equity [Line Items]
Comprehensive income (loss)	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Equity Forward Agreements [Member]
Common Equity [Line Items]
Common stock issued during the period, equity forward agreements (in shares)			3,790,300
Forward sales price (in dollars per share)	$ 43.99		$ 43.99			$ 44.33
Proceeds from issuance of common stock, net			$ 167.0
Shares included in diluted earnings per share (in shares)			671,237
Forecast [Member] | Equity Forward Agreements [Member]
Common Equity [Line Items]
Common stock issued during the period, equity forward agreements (in shares)					8,358,973

XML

Revenues (Tables)

9 Months Ended

Sep. 30, 2019

Disaggregation of Revenue [Line Items]

Disaggregation of Revenue

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

IPL [Member]

Disaggregation of Revenue [Line Items]

Disaggregation of Revenue

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

WPL [Member]

Disaggregation of Revenue [Line Items]

Disaggregation of Revenue

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

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Related Parties

9 Months Ended

Sep. 30, 2019

Related Party Transactions [Line Items]

Related Parties

RELATED PARTIES

Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
ATC billings to WPL		$28		$26		$82		$79
WPL billings to ATC	3		3		10		8

WPL owed ATC net amounts of $9 million as of September 30, 2019 and $8 million as of December 31, 2018.

WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 7 for discussion of WPL’s Sheboygan Falls Energy Facility lease.

IPL [Member]

Related Party Transactions [Line Items]

Related Parties

RELATED PARTIES

Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

WPL [Member]

Related Party Transactions [Line Items]

Related Parties

RELATED PARTIES

Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
ATC billings to WPL		$28		$26		$82		$79
WPL billings to ATC	3		3		10		8

WPL owed ATC net amounts of $9 million as of September 30, 2019 and $8 million as of December 31, 2018.

WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 7 for discussion of WPL’s Sheboygan Falls Energy Facility lease.

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Investments and Acquisitions (Tables)

9 Months Ended

Sep. 30, 2019

Schedule of Investments [Line Items]

Unconsolidated Equity Investments

Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):

	Three Months						Nine Months
	2019			2018			2019			2018
ATC Holdings		($10.5	)		($8.9	)		($30.0	)		($25.4	)
Non-utility wind farm in Oklahoma	(0.4		)	0.1			(2.8		)	(14.5		)
Other	(0.7		)	(1.0		)	(2.4		)	(1.7		)
		($11.6	)		($9.8	)		($35.2	)		($41.6	)

XML

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 193.7	$ 20.9
Accounts receivable, less allowance for doubtful accounts	451.5	350.4
Production fuel, at weighted average cost	71.1	61.4
Gas stored underground, at weighted average cost	46.1	49.0
Materials and supplies, at weighted average cost	106.9	101.4
Regulatory assets	76.3	79.8
Prepaid gross receipts tax	30.3	42.2
Other	137.1	80.0
Total current assets	1,113.0	785.1
Property, plant and equipment, net	13,131.1	12,462.4
Investments:
ATC Holdings	309.1	293.6
Other	143.9	137.7
Total investments	453.0	431.3
Other assets:
Regulatory assets	1,763.7	1,657.5
Deferred charges and other	72.6	89.7
Total other assets	1,836.3	1,747.2
Total assets	16,533.4	15,426.0
Current liabilities:
Current maturities of long-term debt	656.8	256.5
Commercial paper	349.6	441.2
Accounts payable	497.7	543.3
Regulatory liabilities	188.9	142.7
Other	389.1	260.4
Total current liabilities	2,082.1	1,644.1
Long-term debt, net (excluding current portion)	5,535.1	5,246.3
Other liabilities:
Deferred tax liabilities	1,703.0	1,603.1
Regulatory liabilities	1,262.1	1,350.5
Pension and other benefit obligations	476.3	509.1
Other	305.6	287.2
Total other liabilities	3,747.0	3,749.9
Commitments and contingencies (Note 14)
Common equity:
Common stock	2.4	2.4
Additional paid-in capital	2,236.9	2,045.5
Retained earnings	2,739.1	2,545.9
Accumulated other comprehensive income	1.0	1.7
Shares in deferred compensation trust - 385,343 and 384,580 shares at a weighted average cost of $26.52 and $25.60 per share	(10.2)	(9.8)
Total common equity	4,969.2	4,585.7
Cumulative preferred stock of Interstate Power and Light Company	200.0	200.0
Total equity	5,169.2	4,785.7
Total liabilities and equity	16,533.4	15,426.0
IPL [Member]
Current assets:
Cash and cash equivalents	184.0	9.7
Accounts receivable, less allowance for doubtful accounts	258.3	153.5
Production fuel, at weighted average cost	40.3	44.8
Gas stored underground, at weighted average cost	21.6	26.1
Materials and supplies, at weighted average cost	60.3	55.4
Regulatory assets	34.6	39.2
Other	22.1	43.1
Total current assets	621.2	371.8
Property, plant and equipment, net	7,283.9	6,781.5
Other assets:
Regulatory assets	1,369.4	1,239.8
Deferred charges and other	28.1	18.3
Total other assets	1,397.5	1,258.1
Total assets	9,302.6	8,411.4
Current liabilities:
Current maturities of long-term debt	200.0	0.0
Commercial paper	0.0	50.4
Accounts payable	290.0	304.9
Accounts payable to associated companies	40.7	28.8
Regulatory liabilities	95.5	90.0
Accrued taxes	58.7	45.8
Other	197.7	87.2
Total current liabilities	882.6	607.1
Long-term debt, net (excluding current portion)	2,946.8	2,552.3
Other liabilities:
Deferred tax liabilities	974.9	957.3
Regulatory liabilities	638.1	664.9
Pension and other benefit obligations	165.1	178.4
Other	251.0	220.7
Total other liabilities	2,029.1	2,021.3
Commitments and contingencies (Note 14)
Common equity:
Common stock	33.4	33.4
Additional paid-in capital	2,322.8	2,222.8
Retained earnings	887.9	774.5
Total common equity	3,244.1	3,030.7
Cumulative preferred stock of Interstate Power and Light Company	200.0	200.0
Total equity	3,444.1	3,230.7
Total liabilities and equity	9,302.6	8,411.4
WPL [Member]
Current assets:
Cash and cash equivalents	8.3	8.7
Accounts receivable, less allowance for doubtful accounts	184.3	190.1
Production fuel, at weighted average cost	30.8	16.6
Gas stored underground, at weighted average cost	24.5	22.9
Materials and supplies, at weighted average cost	43.7	42.9
Regulatory assets	41.7	40.6
Prepaid gross receipts tax	30.3	42.2
Other	86.6	20.6
Total current assets	450.2	384.6
Property, plant and equipment, net	5,449.7	5,287.3
Other assets:
Regulatory assets	394.3	417.7
Deferred charges and other	19.5	62.9
Total other assets	413.8	480.6
Total assets	6,313.7	6,152.5
Current liabilities:
Current maturities of long-term debt	150.0	250.0
Commercial paper	0.0	105.5
Accounts payable	151.1	180.9
Regulatory liabilities	93.4	52.7
Other	113.6	105.5
Total current liabilities	508.1	694.6
Long-term debt, net (excluding current portion)	1,782.3	1,584.9
Other liabilities:
Deferred tax liabilities	652.6	582.0
Regulatory liabilities	624.0	685.6
Finance lease obligations - Sheboygan Falls Energy Facility	53.6	60.0
Pension and other benefit obligations	203.5	217.7
Other	164.8	178.2
Total other liabilities	1,698.5	1,723.5
Commitments and contingencies (Note 14)
Common equity:
Common stock	66.2	66.2
Additional paid-in capital	1,409.0	1,309.0
Retained earnings	849.6	774.3
Total common equity	2,324.8	2,149.5
Total equity	2,324.8	2,149.5
Total liabilities and equity	$ 6,313.7	$ 6,152.5

XML

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Statement [Line Items]

Fair Value Measurements

Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

IPL [Member]

Statement [Line Items]

Fair Value Measurements

Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

WPL [Member]

Statement [Line Items]

Fair Value Measurements

Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

XML

Income Taxes (Tables)

9 Months Ended

Sep. 30, 2019

Income Taxes [Line Items]

Schedule Of Effective Income Tax Rates

The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

Summary Of Tax Credit Carryforwards

At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

IPL [Member]

Income Taxes [Line Items]

Schedule Of Effective Income Tax Rates

The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

Summary Of Tax Credit Carryforwards

At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

WPL [Member]

Income Taxes [Line Items]

Schedule Of Effective Income Tax Rates

The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

Summary Of Tax Credit Carryforwards

At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

XML

Regulatory Matters

9 Months Ended

Sep. 30, 2019

Public Utilities, General Disclosures [Line Items]

Regulatory Matters

REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

Assets Retired Early - Upon completion of the phased installation of advanced metering infrastructure, IPL retired certain analog electric meters in September 2019 and reclassified the $36 million remaining net book value of these meters from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. Recovery of these retired meters is included in the settlement agreement for IPL’s current retail electric base rate increase, and the IUB will decide on the recovery of these assets with the current retail electric rate review decision.

IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by 5 years. The IUB approved placing the buyout payment in a regulatory asset account, which will be recovered from IPL’s retail customers over a 5-year period following the payment. The offsetting obligation has been discounted and is recorded in “Other current liabilities” on Alliant Energy’s and IPL’s balance sheets.

Utility Rate Reviews

IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million, on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision.

In October 2019, IPL reached a partial, non-unanimous settlement agreement with intervenor groups for an annual retail electric base rate increase of $127 million. The agreement includes both the recovery of and a return on IPL’s early retired EGUs, and the recovery of IPL’s retired analog electric meters. The settlement agreement also includes IPL providing billing credits over a 12-month period beginning with final rates, including $27 million of excess deferred taxes resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform and $8 million from a partial refund of interim rates implemented in 2019.

The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision, including a decision on the settlement agreement, from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.

IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects. In October 2019, IPL reached a unanimous settlement agreement with intervenor groups for an annual retail gas base rate increase of $12 million. IPL currently expects a decision, including a decision on the settlement agreement, from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.

IPL [Member]

Public Utilities, General Disclosures [Line Items]

Regulatory Matters

REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

Assets Retired Early - Upon completion of the phased installation of advanced metering infrastructure, IPL retired certain analog electric meters in September 2019 and reclassified the $36 million remaining net book value of these meters from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. Recovery of these retired meters is included in the settlement agreement for IPL’s current retail electric base rate increase, and the IUB will decide on the recovery of these assets with the current retail electric rate review decision.

IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by 5 years. The IUB approved placing the buyout payment in a regulatory asset account, which will be recovered from IPL’s retail customers over a 5-year period following the payment. The offsetting obligation has been discounted and is recorded in “Other current liabilities” on Alliant Energy’s and IPL’s balance sheets.

Utility Rate Reviews

IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million, on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision.

In October 2019, IPL reached a partial, non-unanimous settlement agreement with intervenor groups for an annual retail electric base rate increase of $127 million. The agreement includes both the recovery of and a return on IPL’s early retired EGUs, and the recovery of IPL’s retired analog electric meters. The settlement agreement also includes IPL providing billing credits over a 12-month period beginning with final rates, including $27 million of excess deferred taxes resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform and $8 million from a partial refund of interim rates implemented in 2019.

The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision, including a decision on the settlement agreement, from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.

IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects. In October 2019, IPL reached a unanimous settlement agreement with intervenor groups for an annual retail gas base rate increase of $12 million. IPL currently expects a decision, including a decision on the settlement agreement, from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.

WPL [Member]

Public Utilities, General Disclosures [Line Items]

Regulatory Matters

REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

XML

Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 174.4	$ 0.0
Money market fund investments interest rate, percentage	2.00%
IPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 173.7	$ 0.0
Money market fund investments interest rate, percentage	2.00%

XML

Revenues

9 Months Ended

Sep. 30, 2019

Disaggregation of Revenue [Line Items]

Revenue from Contract with Customer

REVENUES

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

IPL [Member]

Disaggregation of Revenue [Line Items]

Revenue from Contract with Customer

REVENUES

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

WPL [Member]

Disaggregation of Revenue [Line Items]

Revenue from Contract with Customer

REVENUES

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$331.6		$312.9		$196.0		$180.1		$135.6		$132.8
Retail - commercial	230.9		215.4		158.4		146.0		72.5		69.4
Retail - industrial	263.4		247.8		157.5		141.4		105.9		106.4
Wholesale	49.8		50.0		17.7		18.2		32.1		31.8
Bulk power and other	40.2		35.1		31.3		23.5		8.9		11.6
Total Electric Utility	915.9		861.2		560.9		509.2		355.0		352.0
Gas Utility:
Retail - residential	20.4		21.8		11.7		12.6		8.7		9.2
Retail - commercial	10.0		11.0		5.9		6.4		4.1		4.6
Retail - industrial	2.3		3.0		1.9		2.0		0.4		1.0
Transportation/other	8.8		9.0		5.3		5.7		3.5		3.3
Total Gas Utility	41.5		44.8		24.8		26.7		16.7		18.1
Other Utility:
Steam	9.1		8.7		9.1		8.7		—		—
Other utility	2.1		3.6		1.7		3.0		0.4		0.6
Total Other Utility	11.2		12.3		10.8		11.7		0.4		0.6
Non-Utility and Other:
Transportation and other	21.6		10.3		—		—		—		—
Total Non-Utility and Other	21.6		10.3		—		—		—		—
Total revenues		$990.2		$928.6		$596.5		$547.6		$372.1		$370.7

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Electric Utility:
Retail - residential		$839.6		$820.6		$469.4		$461.6		$370.2		$359.0
Retail - commercial	583.3		561.7		386.4		371.8		196.9		189.9
Retail - industrial	686.3		675.1		392.0		385.0		294.3		290.1
Wholesale	137.3		146.9		49.2		56.4		88.1		90.5
Bulk power and other	104.0		91.9		76.0		62.2		28.0		29.7
Total Electric Utility	2,350.5		2,296.2		1,373.0		1,337.0		977.5		959.2
Gas Utility:
Retail - residential	187.4		170.1		109.6		100.9		77.8		69.2
Retail - commercial	89.7		87.3		49.5		49.8		40.2		37.5
Retail - industrial	9.7		11.4		6.7		6.1		3.0		5.3
Transportation/other	35.7		30.2		22.0		20.2		13.7		10.0
Total Gas Utility	322.5		299.0		187.8		177.0		134.7		122.0
Other Utility:
Steam	26.7		26.5		26.7		26.5		—		—
Other utility	6.5		9.7		5.3		7.7		1.2		2.0
Total Other Utility	33.2		36.2		32.0		34.2		1.2		2.0
Non-Utility and Other:
Transportation and other	61.4		29.6		—		—		—		—
Total Non-Utility and Other	61.4		29.6		—		—		—		—
Total revenues		$2,767.6		$2,661.0		$1,592.8		$1,548.2		$1,113.4		$1,083.2

XML

Derivative Instruments

9 Months Ended

Sep. 30, 2019

Derivative Instruments [Line Items]

Derivative Instruments

DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Notional Amounts - As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At September 30, 2019 and December 31, 2018, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at September 30, 2019 and December 31, 2018. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

IPL [Member]

Derivative Instruments [Line Items]

Derivative Instruments

DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Notional Amounts - As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At September 30, 2019 and December 31, 2018, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at September 30, 2019 and December 31, 2018. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

WPL [Member]

Derivative Instruments [Line Items]

Derivative Instruments

DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Notional Amounts - As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At September 30, 2019 and December 31, 2018, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at September 30, 2019 and December 31, 2018. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

XML

Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Administrative and General Services Billings [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 47	$ 43	$ 137	$ 128
Administrative and General Services Billings [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	36	33	104	100
Sales Credited [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	23	11	50	34
Sales Credited [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	2	7	6	16
Purchases Billed [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	93	95	251	268
Purchases Billed [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 32	$ 19	$ 91	$ 56

XML

Commitments And Contingencies (Other Purchase Commitments) (Details) - USD ($) $ in Millions		1 Months Ended	9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Commitments and Contingencies [Line Items]
Minimum future commitments			$ 1,230
Individual commitments incurred			1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			723
Individual commitments incurred			1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			498
Individual commitments incurred			1
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]		145
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]		144
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]		1
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			892
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			460
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			432
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[2]		117
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[2]		76
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[2]		41
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[3]		76
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[3]		43
Other [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[3]		$ 24
Forecast [Member] | DAEC PPA [Member]
Commitments and Contingencies [Line Items]
Buyout payment		$ 110

[1] Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

[2] Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

[3] Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

XML

Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 990.2	$ 928.6	$ 2,767.6	$ 2,661.0
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	915.9	861.2	2,350.5	2,296.2
Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	331.6	312.9	839.6	820.6
Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	230.9	215.4	583.3	561.7
Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	263.4	247.8	686.3	675.1
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	49.8	50.0	137.3	146.9
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	40.2	35.1	104.0	91.9
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	41.5	44.8	322.5	299.0
Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20.4	21.8	187.4	170.1
Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10.0	11.0	89.7	87.3
Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2.3	3.0	9.7	11.4
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8.8	9.0	35.7	30.2
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11.2	12.3	33.2	36.2
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9.1	8.7	26.7	26.5
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2.1	3.6	6.5	9.7
Non-utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	21.6	10.3	61.4	29.6
Non-utility and Other [Member] | Transportation and other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	21.6	10.3	61.4	29.6
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	596.5	547.6	1,592.8	1,548.2
IPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	560.9	509.2	1,373.0	1,337.0
IPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	196.0	180.1	469.4	461.6
IPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	158.4	146.0	386.4	371.8
IPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	157.5	141.4	392.0	385.0
IPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	17.7	18.2	49.2	56.4
IPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	31.3	23.5	76.0	62.2
IPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24.8	26.7	187.8	177.0
IPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11.7	12.6	109.6	100.9
IPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5.9	6.4	49.5	49.8
IPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1.9	2.0	6.7	6.1
IPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5.3	5.7	22.0	20.2
IPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10.8	11.7	32.0	34.2
IPL [Member] | Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9.1	8.7	26.7	26.5
IPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1.7	3.0	5.3	7.7
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	372.1	370.7	1,113.4	1,083.2
WPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	355.0	352.0	977.5	959.2
WPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	135.6	132.8	370.2	359.0
WPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	72.5	69.4	196.9	189.9
WPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	105.9	106.4	294.3	290.1
WPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32.1	31.8	88.1	90.5
WPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8.9	11.6	28.0	29.7
WPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16.7	18.1	134.7	122.0
WPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8.7	9.2	77.8	69.2
WPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4.1	4.6	40.2	37.5
WPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0.4	1.0	3.0	5.3
WPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3.5	3.3	13.7	10.0
WPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0.4	0.6	1.2	2.0
WPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0.4	$ 0.6	$ 1.2	$ 2.0

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Debt (Narrative) (Details) - USD ($)	1 Months Ended				9 Months Ended
	Sep. 30, 2019	Jul. 31, 2019	Jun. 30, 2019	Apr. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Debt [Line Items]
Credit facility agreement, extension					1 year
Line of credit facility, current borrowing capacity	$ 1,000,000,000				$ 1,000,000,000
Payments to retire long-term debt					253,500,000	$ 603,100,000
IPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	250,000,000				250,000,000
Payments to retire long-term debt					0	100,000,000.0
WPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	$ 300,000,000				300,000,000
Payments to retire long-term debt					$ 250,000,000.0	$ 0
Senior Debentures [Member] | 3.6% senior debentures due 2029 [Member] | IPL [Member]
Debt [Line Items]
Proceeds from issuance of long-term debt				$ 300,000,000
Interest rate, percent	3.60%				3.60%
Senior Debentures [Member] | 3.5% senior debentures due 2049 [Member] | IPL [Member]
Debt [Line Items]
Proceeds from issuance of long-term debt	$ 300,000,000
Interest rate, percent	3.50%				3.50%
Debentures [Member] | 3% debentures due 2029 [Member] | WPL [Member]
Debt [Line Items]
Proceeds from issuance of long-term debt			$ 350,000,000
Interest rate, percent	3.00%				3.00%
Debentures [Member] | 5% debentures due 2019 [Member] | WPL [Member]
Debt [Line Items]
Interest rate, percent			5.00%
Payments to retire long-term debt		$ 250,000,000
Parent Company [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	$ 450,000,000				$ 450,000,000

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Leases (Operating Leases) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 17	$ 17
Operating leases liabilities, Other current liabilities	2	2
Operating leases liabilities, Other liabilities	15	15
Operating leases liabilities, Total	$ 17	$ 17
Operating Lease, Weighted average remaining lease term	11 years	11 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 1	$ 2
IPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	10	10
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	9	9
Operating leases liabilities, Total	$ 10	$ 10
Operating Lease, Weighted average remaining lease term	12 years	12 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 1	$ 1
WPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	7	7
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	6	6
Operating leases liabilities, Total	$ 7	$ 7
Operating Lease, Weighted average remaining lease term	10 years	10 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating leases, Cost	$ 0	$ 0

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Investments and Acquisitions (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Schedule of Investments [Line Items]
Acquisitions of freight management companies	$ 21
Contingent consideration	$ 8
Contingent consideration, expected payment timing	2 years

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Receivables (Narrative) (Details) - Receivables Sold [Member] - IPL [Member] $ in Millions	Sep. 30, 2019 USD ($)
Receivables [Line Items]
Available capacity	$ 109.0
Outstanding receivables past due	$ 26.6

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Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Sep. 30, 2019 USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 611
Tax credits, carryforward amount	337
Federal [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	522
Tax credits, carryforward amount	162
Federal [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	41
Tax credits, carryforward amount	156
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	677
State [Member] | IPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	12
State [Member] | WPL [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2

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Asset Retirement Obligations (Reconciliation Of Changes In Asset Retirement Obligations) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	$ 177.5
Revisions in estimated cash flows	(5.8)
Liabilities settled	(5.9)
Liabilities incurred	26.2	[1]
Accretion expense	5.3
Balance, September 30	197.3
IPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	118.3
Revisions in estimated cash flows	(7.0)
Liabilities settled	(5.6)
Liabilities incurred	26.2	[1]
Accretion expense	3.5
Balance, September 30	$ 135.4

[1] During the nine months ended September 30, 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

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Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 13.2	$ (10.7)	$ 12.2	$ (12.2)
Total net gains (losses) included in changes in net assets (realized/unrealized)		12.7	25.7	6.9	15.7
Transfers out of Level 3		(1.2)	15.6	2.8	15.6
Purchases				13.8	26.7
Sales		0.0	(0.2)	(0.2)	(0.2)
Settlements		(3.0)	(6.2)	(13.8)	(21.4)
Ending balance		21.7	24.2	21.7	24.2
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		12.7	26.1	10.1	16.5
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		9.3	(4.1)	9.0	(1.4)
Total net gains (losses) included in changes in net assets (realized/unrealized)		11.5	16.8	8.6	7.6
Transfers out of Level 3		(0.6)	10.5	2.0	10.5
Purchases				9.5	19.3
Sales		0.0	(0.1)	(0.1)	(0.1)
Settlements		(2.2)	(4.9)	(11.0)	(17.7)
Ending balance		18.0	18.2	18.0	18.2
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		11.5	16.8	10.5	7.9
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		3.9	(6.6)	3.2	(10.8)
Total net gains (losses) included in changes in net assets (realized/unrealized)		1.2	8.9	(1.7)	8.1
Transfers out of Level 3		(0.6)	5.1	0.8	5.1
Purchases				4.3	7.4
Sales		0.0	(0.1)	(0.1)	(0.1)
Settlements		(0.8)	(1.3)	(2.8)	(3.7)
Ending balance		3.7	6.0	3.7	6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		1.2	9.3	(0.4)	8.6
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		214.6	208.3	119.4	222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)		0.0	0.0	0.0	0.0
Transfers out of Level 3		0.0	0.0	0.0	0.0
Purchases				0.0	0.0
Sales		0.0	0.0	0.0	0.0
Settlements	[1]	22.4	35.4	117.6	21.6
Ending balance		237.0	243.7	237.0	243.7
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		0.0	0.0	0.0	0.0
Deferred Proceeds [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		214.6	208.3	119.4	222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)		0.0	0.0	0.0	0.0
Transfers out of Level 3		0.0	0.0	0.0	0.0
Purchases				0.0	0.0
Sales		0.0	0.0	0.0	0.0
Settlements	[1]	22.4	35.4	117.6	21.6
Ending balance		237.0	243.7	237.0	243.7
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		$ 0.0	$ 0.0	$ 0.0	$ 0.0

[1] Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

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Regulatory Matters (Tables)

9 Months Ended

Sep. 30, 2019

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

XML

Debt (Tables)

9 Months Ended

Sep. 30, 2019

Short-term Debt [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

IPL [Member]

Short-term Debt [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

WPL [Member]

Short-term Debt [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

XML

Debt

9 Months Ended

Sep. 30, 2019

Debt [Line Items]

Debt

DEBT

NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year, which currently expires in August 2023. As of September 30, 2019, the short-term borrowing capacity under the agreement totaled $1 billion ($450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. In September 2019, IPL issued $300 million of 3.50% senior debentures due 2049. The senior debentures were issued as green bonds, and all of the net proceeds have been or will be allocated for the construction and development of IPL’s wind projects.

In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.

IPL [Member]

Debt [Line Items]

Debt

DEBT

NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year, which currently expires in August 2023. As of September 30, 2019, the short-term borrowing capacity under the agreement totaled $1 billion ($450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. In September 2019, IPL issued $300 million of 3.50% senior debentures due 2049. The senior debentures were issued as green bonds, and all of the net proceeds have been or will be allocated for the construction and development of IPL’s wind projects.

In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.

WPL [Member]

Debt [Line Items]

Debt

DEBT

NOTE 6(a) Short-term Debt - In March 2019, Alliant Energy, IPL and WPL extended their single credit facility agreement by one year, which currently expires in August 2023. As of September 30, 2019, the short-term borrowing capacity under the agreement totaled $1 billion ($450 million for Alliant Energy at the parent company, $250 million for IPL and $300 million for WPL). Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

September 30, 2019	Alliant Energy	IPL	WPL
Commercial paper outstanding	$349.6	$—	$—
Commercial paper weighted average interest rates	2.3%	N/A	N/A
Available credit facility capacity	$650.4	$250.0	$300.0

	Alliant Energy		IPL		WPL
Three Months Ended September 30	2019	2018	2019	2018	2019	2018
Maximum amount outstanding (based on daily outstanding balances)	$471.7	$153.3	$—	$—	$89.7	$75.4
Average amount outstanding (based on daily outstanding balances)	$399.5	$80.8	$—	$—	$27.0	$23.1
Weighted average interest rates	2.5%	2.2%	N/A	N/A	2.3%	2.0%
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$600.6	$446.5	$50.4	$31.4	$195.1	$109.4
Average amount outstanding (based on daily outstanding balances)	$476.3	$207.6	$0.2	$1.7	$101.8	$26.6
Weighted average interest rates	2.6%	2.1%	2.8%	2.3%	2.5%	1.9%

NOTE 6(b) Long-term Debt - In April 2019, IPL issued $300 million of 3.60% senior debentures due 2029. In September 2019, IPL issued $300 million of 3.50% senior debentures due 2049. The senior debentures were issued as green bonds, and all of the net proceeds have been or will be allocated for the construction and development of IPL’s wind projects.

In June 2019, WPL issued $350 million of 3.00% debentures due 2029. The net proceeds from the issuance were used by WPL to reduce its outstanding commercial paper and retire its $250 million 5% debentures that matured in July 2019.

XML

Benefit Plans

9 Months Ended

Sep. 30, 2019

Benefit Plans

BENEFIT PLANS

NOTE 10(a) Pension and OPEB Plans -

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

As of September 30, 2019, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $7.2 million, $4.0 million and $2.9 million, respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years.

For the nine months ended September 30, 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3-year performance period. For the nine months ended September 30, 2019, 91,816 performance shares were granted with a weighted average grant date fair value of $47.23. The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3-year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3-year time-vesting period. For the nine months ended September 30, 2019, 91,816 performance restricted stock units were granted with a weighted average grant date fair value of $46.10, and 105,348 restricted stock units were granted with a weighted average grant date fair value of $45.98, which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of September 30, 2019, 122,720 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

IPL [Member]

Benefit Plans

BENEFIT PLANS

NOTE 10(a) Pension and OPEB Plans -

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

As of September 30, 2019, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $7.2 million, $4.0 million and $2.9 million, respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years.

For the nine months ended September 30, 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3-year performance period. For the nine months ended September 30, 2019, 91,816 performance shares were granted with a weighted average grant date fair value of $47.23. The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3-year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3-year time-vesting period. For the nine months ended September 30, 2019, 91,816 performance restricted stock units were granted with a weighted average grant date fair value of $46.10, and 105,348 restricted stock units were granted with a weighted average grant date fair value of $45.98, which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of September 30, 2019, 122,720 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

WPL [Member]

Benefit Plans

BENEFIT PLANS

NOTE 10(a) Pension and OPEB Plans -

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 30 are included below (in millions). For IPL and WPL, amounts represent their current and former employees covered under plans they sponsor, as well as amounts directly assigned to them related to their current and former employees who are participants in the Alliant Energy and Corporate Services sponsored plans.

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
Alliant Energy	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$2.5			$3.1			$7.3			$9.1			$0.8			$1.0			$2.5			$3.1
Interest cost	12.5			11.7			37.4			35.1			2.2			2.0			6.4			5.8
Expected return on plan assets	(15.1		)	(17.4		)	(45.1		)	(52.3		)	(1.2		)	(1.5		)	(3.7		)	(4.5		)
Amortization of prior service credit	(0.2		)	(0.2		)	(0.5		)	(0.5		)	(0.1		)	—			(0.2		)	(0.1		)
Amortization of actuarial loss	9.1			8.8			27.3			26.4			0.8			0.8			2.4			2.5
		$8.8			$6.0			$26.4			$17.8			$2.5			$2.3			$7.4			$6.8

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
IPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$1.6			$1.8			$4.6			$5.5			$0.3			$0.4			$1.0			$1.3
Interest cost	5.6			5.3			17.0			16.0			0.8			0.7			2.5			2.3
Expected return on plan assets	(7.0		)	(8.1		)	(21.1		)	(24.4		)	(0.9		)	(1.1		)	(2.7		)	(3.3		)
Amortization of prior service credit	(0.1		)	—			(0.2		)	(0.1		)	—			—			—			—
Amortization of actuarial loss	3.9			3.7			11.8			11.2			0.4			0.4			1.1			1.0
		$4.0			$2.7			$12.1			$8.2			$0.6			$0.4			$1.9			$1.3

	Defined Benefit Pension Plans												OPEB Plans
	Three Months						Nine Months						Three Months						Nine Months
WPL	2019			2018			2019			2018			2019			2018			2019			2018
Service cost		$0.9			$1.1			$2.6			$3.3			$0.3			$0.4			$0.9			$1.2
Interest cost	5.3			5.0			16.1			15.1			0.9			0.8			2.6			2.3
Expected return on plan assets	(6.5		)	(7.6		)	(19.6		)	(22.8		)	(0.2		)	(0.2		)	(0.5		)	(0.5		)
Amortization of prior service credit	—			—			(0.1		)	(0.1		)	—			—			(0.1		)	(0.1		)
Amortization of actuarial loss	4.4			4.3			13.2			12.9			0.4			0.5			1.2			1.5
		$4.1			$2.8			$12.2			$8.4			$1.4			$1.5			$4.1			$4.4

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy								IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018		2019		2018		2019		2018
Compensation expense		$7.5		$4.2		$15.6		$12.6		$4.2		$2.4		$8.7		$7.0		$3.0		$1.7		$6.2		$5.1
Income tax benefits	2.1		1.2		4.4		3.6		1.2		0.7		2.5		2.1		0.8		0.5		1.7		1.4

As of September 30, 2019, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $7.2 million, $4.0 million and $2.9 million, respectively, which is expected to be recognized over a weighted average period of between 1 and 2 years.

For the nine months ended September 30, 2019, performance shares, performance restricted stock units and restricted stock units were granted to key employees and will be paid out in shares, and are therefore accounted for as equity awards. The 2019 performance shares contain a market condition based on total shareowner return relative to an investor-owned utility peer group. The fair value of each performance share is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a 3-year performance period. For the nine months ended September 30, 2019, 91,816 performance shares were granted with a weighted average grant date fair value of $47.23. The 2019 performance restricted stock units will vest based on the achievement of certain targets (specified growth of consolidated net income from continuing operations) during a 3-year performance period. The actual number of performance shares and performance restricted units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares or units, as applicable. The 2019 restricted stock units will vest based on the expiration of a 3-year time-vesting period. For the nine months ended September 30, 2019, 91,816 performance restricted stock units were granted with a weighted average grant date fair value of $46.10, and 105,348 restricted stock units were granted with a weighted average grant date fair value of $45.98, which is based on the closing market price of one share of Alliant Energy’s common stock on the grant date of the award. As of September 30, 2019, 122,720 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

XML

Commitments And Contingencies

9 Months Ended

Sep. 30, 2019

Commitments and Contingencies Disclosure

COMMITMENTS AND CONTINGENCIES

NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s and WPL’s projects include the expansion of wind generation, and WPL’s projects also include the West Riverside Energy Center. At September 30, 2019, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $124 million, $79 million and $45 million, respectively.

NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

NOTE 14(c) Guarantees and Indemnifications -

Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of September 30, 2019, the present value of the abandonment obligations is estimated at $38 million. Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of September 30, 2019 and December 31, 2018.

Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $82 million as of September 30, 2019 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of September 30, 2019 and December 31, 2018.

IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of September 30, 2019 and December 31, 2018. The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020.

NOTE 14(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2019, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At September 30, 2019, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$14	-	$31		$12	-	$25
Current and non-current environmental liabilities	19				16

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.

Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act.

Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters.

NOTE 14(e) Collective Bargaining Agreements - At September 30, 2019, employees covered by collective bargaining agreements represented 54%, 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. In November 2019, the parties reached a new agreement, which expires May 31, 2022.

IPL [Member]

Commitments and Contingencies Disclosure

COMMITMENTS AND CONTINGENCIES

NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s and WPL’s projects include the expansion of wind generation, and WPL’s projects also include the West Riverside Energy Center. At September 30, 2019, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $124 million, $79 million and $45 million, respectively.

NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

NOTE 14(c) Guarantees and Indemnifications -

Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of September 30, 2019, the present value of the abandonment obligations is estimated at $38 million. Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of September 30, 2019 and December 31, 2018.

Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $82 million as of September 30, 2019 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of September 30, 2019 and December 31, 2018.

IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of September 30, 2019 and December 31, 2018. The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020.

NOTE 14(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2019, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At September 30, 2019, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$14	-	$31		$12	-	$25
Current and non-current environmental liabilities	19				16

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.

Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act.

Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters.

NOTE 14(e) Collective Bargaining Agreements - At September 30, 2019, employees covered by collective bargaining agreements represented 54%, 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. In November 2019, the parties reached a new agreement, which expires May 31, 2022.

WPL [Member]

Commitments and Contingencies Disclosure

COMMITMENTS AND CONTINGENCIES

NOTE 14(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects. IPL’s and WPL’s projects include the expansion of wind generation, and WPL’s projects also include the West Riverside Energy Center. At September 30, 2019, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $124 million, $79 million and $45 million, respectively.

NOTE 14(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2019, the related minimum future commitments were as follows (in millions):

	Alliant Energy		IPL		WPL
Purchased power (a)		$145		$144		$1
Natural gas	892		460		432
Coal (b)	117		76		41
Other (c)	76		43		24
		$1,230		$723		$498

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2019 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2019.

NOTE 14(c) Guarantees and Indemnifications -

Whiting Petroleum - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Whiting Petroleum is an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under general partnership agreements in the oil and gas industry, including with respect to the future abandonment of certain platforms off the coast of California and related onshore plant and equipment owned by the partnerships. The guarantees do not include a maximum limit. As of September 30, 2019, the present value of the abandonment obligations is estimated at $38 million. Alliant Energy is not aware of any material liabilities related to these guarantees of which it is probable that Alliant Energy Resources, LLC will be obligated to pay and therefore has not recognized any material liabilities related to these guarantees as of September 30, 2019 and December 31, 2018.

Non-utility Wind Farm in Oklahoma - In July 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $82 million as of September 30, 2019 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of September 30, 2019 and December 31, 2018.

IPL’s Minnesota Electric Distribution Assets - IPL provided indemnifications associated with the 2015 sale of its Minnesota electric distribution assets for losses resulting from potential breach of IPL’s representations, warranties and obligations under the sale agreement. Alliant Energy and IPL believe the likelihood of having to make any material cash payments under these indemnifications is remote. IPL has not recorded any material liabilities related to these indemnifications as of September 30, 2019 and December 31, 2018. The general terms of the indemnifications provided by IPL included a maximum limit of $17 million and expire in October 2020.

NOTE 14(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2019, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At September 30, 2019, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$14	-	$31		$12	-	$25
Current and non-current environmental liabilities	19				16

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Burlington by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.

Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however future capital investments and/or modifications to EGUs to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act.

Clean Air Act Section 111(d) - In July 2019, the EPA published the final Affordable Clean Energy rule, which repeals the Clean Power Plan effective September 6, 2019. The final rule establishes emission guidelines for states to develop plans by July 2022 to reduce carbon dioxide emissions from existing coal-fired EGUs, and is subject to legal challenges. Alliant Energy, IPL and WPL are currently unable to predict with certainty the final outcome or impact of these matters.

NOTE 14(e) Collective Bargaining Agreements - At September 30, 2019, employees covered by collective bargaining agreements represented 54%, 60% and 82% of total employees of Alliant Energy, IPL and WPL, respectively. On May 31, 2019, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 27% and 82% of total employees of Alliant Energy and WPL, respectively. In November 2019, the parties reached a new agreement, which expires May 31, 2022.

XML

Document And Entity Information	9 Months Ended
	Sep. 30, 2019 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity Registrant Name	ALLIANT ENERGY CORP
Entity Central Index Key	0000352541
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	1-9894
Entity Tax Identification Number	39-1380265
Title of 12(b) Security	Common Stock, $0.01 Par Value
Trading Symbol	LNT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	240,342,949
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
IPL [Member]
Entity Information [Line Items]
Entity Registrant Name	INTERSTATE POWER & LIGHT CO
Entity Central Index Key	0000052485
Entity Incorporation, State or Country Code	IA
Entity Address, Address Line One	Alliant Energy Tower
Entity Address, City or Town	Cedar Rapids
Entity Address, State or Province	IA
Entity Address, Postal Zip Code	52401
City Area Code	319
Local Phone Number	786-4411
Entity File Number	1-4117
Entity Tax Identification Number	42-0331370
Title of 12(b) Security	5.100% Series D Cumulative Perpetual Preferred Stock, $0.01 Par Value
Trading Symbol	IPLDP
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	13,370,788
WPL [Member]
Entity Information [Line Items]
Entity Registrant Name	WISCONSIN POWER & LIGHT CO
Entity Central Index Key	0000107832
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	0-337
Entity Tax Identification Number	39-0714890
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	13,236,601

XML

Segments Of Business (Tables)

9 Months Ended

Sep. 30, 2019

Segment Reporting Information [Line Items]

Schedule Of Segments Of Business

Certain financial information relating to Alliant Energy’s business segments is as follows. Intersegment revenues were not material to Alliant Energy’s operations.

										ATC Holdings,		Alliant
	Utility									Non-Utility,		Energy
	Electric		Gas			Other		Total		Parent and Other		Consolidated
	(in millions)
Three Months Ended September 30, 2019
Revenues		$915.9		$41.5			$11.2		$968.6		$21.6		$990.2
Operating income (loss)	283.7		(4.7		)	2.8		281.8		8.4		290.2
Net income attributable to Alliant Energy common shareowners								216.6		9.4		226.0
Three Months Ended September 30, 2018
Revenues		$861.2		$44.8			$12.3		$918.3		$10.3		$928.6
Operating income (loss)	248.7		(2.0		)	0.6		247.3		8.8		256.1
Net income attributable to Alliant Energy common shareowners								202.8		2.7		205.5

									ATC Holdings,		Alliant
	Utility								Non-Utility,		Energy
	Electric		Gas		Other		Total		Parent and Other		Consolidated
	(in millions)
Nine Months Ended September 30, 2019
Revenues		$2,350.5		$322.5		$33.2		$2,706.2		$61.4		$2,767.6
Operating income	543.0		47.7		4.2		594.9		21.9		616.8
Net income attributable to Alliant Energy common shareowners							422.6		23.1		445.7
Nine Months Ended September 30, 2018
Revenues		$2,296.2		$299.0		$36.2		$2,631.4		$29.6		$2,661.0
Operating income	510.2		34.9		2.9		548.0		25.0		573.0
Net income attributable to Alliant Energy common shareowners							395.0		31.8		426.8

IPL [Member]

Segment Reporting Information [Line Items]

Schedule Of Segments Of Business

Certain financial information relating to IPL’s business segments is as follows. Intersegment revenues were not material to IPL’s operations.

	Electric		Gas			Other		Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$560.9		$24.8			$10.8		$596.5
Operating income (loss)	175.1		(4.2		)	2.6		173.5
Earnings available for common stock								141.1
Three Months Ended September 30, 2018
Revenues		$509.2		$26.7			$11.7		$547.6
Operating income (loss)	144.7		(3.1		)	1.5		143.1
Earnings available for common stock								126.5
Nine Months Ended September 30, 2019
Revenues		$1,373.0		$187.8			$32.0		$1,592.8
Operating income	290.8		26.3			4.4		321.5
Earnings available for common stock								239.4
Nine Months Ended September 30, 2018
Revenues		$1,337.0		$177.0			$34.2		$1,548.2
Operating income	275.7		16.3			4.4		296.4
Earnings available for common stock								224.9

WPL [Member]

Segment Reporting Information [Line Items]

Schedule Of Segments Of Business

Certain financial information relating to WPL’s business segments is as follows. Intersegment revenues were not material to WPL’s operations.

	Electric		Gas			Other			Total
	(in millions)
Three Months Ended September 30, 2019
Revenues		$355.0		$16.7			$0.4			$372.1
Operating income (loss)	108.6		(0.5		)	0.2			108.3
Earnings available for common stock									75.5
Three Months Ended September 30, 2018
Revenues		$352.0		$18.1			$0.6			$370.7
Operating income (loss)	104.0		1.1			(0.9		)	104.2
Earnings available for common stock									76.3
Nine Months Ended September 30, 2019
Revenues		$977.5		$134.7			$1.2			$1,113.4
Operating income (loss)	252.2		21.4			(0.2		)	273.4
Earnings available for common stock									183.2
Nine Months Ended September 30, 2018
Revenues		$959.2		$122.0			$2.0			$1,083.2
Operating income (loss)	234.5		18.6			(1.5		)	251.6
Earnings available for common stock									170.1

XML

Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2019

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation of Changes in Asset Retirement Obligations

A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2019 is as follows (in millions):

	Alliant Energy			IPL
Balance, January 1		$177.5			$118.3
Revisions in estimated cash flows	(5.8		)	(7.0		)
Liabilities settled	(5.9		)	(5.6		)
Liabilities incurred (a)	26.2			26.2
Accretion expense	5.3			3.5
Balance, September 30		$197.3			$135.4

(a)

During the nine months ended September 30, 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

IPL [Member]

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation of Changes in Asset Retirement Obligations

A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2019 is as follows (in millions):

	Alliant Energy			IPL
Balance, January 1		$177.5			$118.3
Revisions in estimated cash flows	(5.8		)	(7.0		)
Liabilities settled	(5.9		)	(5.6		)
Liabilities incurred (a)	26.2			26.2
Accretion expense	5.3			3.5
Balance, September 30		$197.3			$135.4

(a)

During the nine months ended September 30, 2019, Alliant Energy and IPL recognized additional asset retirement obligations related to IPL’s newly constructed Upland Prairie and English Farms wind sites. The increases in asset retirement obligations resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

XML

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 453.4	$ 434.5
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	423.6	376.4
Deferred tax expense and tax credits	53.2	62.5
Equity component of allowance for funds used during construction	(46.3)	(35.5)
Other	17.1	2.1
Other changes in assets and liabilities:
Accounts receivable	(359.2)	(325.2)
Accounts payable	(27.9)	(47.3)
Deferred income taxes	45.4	32.7
Other	(50.1)	(58.0)
Net cash flows from operating activities	509.2	442.2
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(1,003.9)	(1,080.2)
Other construction and acquisition expenditures	(71.4)	(47.8)
Cash receipts on sold receivables	255.9	337.2
Other	(41.7)	(24.9)
Net cash flows used for investing activities	(861.1)	(815.7)
Cash flows from (used for) financing activities:
Common stock dividends	(252.5)	(233.3)
Proceeds from issuance of common stock, net	185.4	191.3
Proceeds from issuance of long-term debt	950.0	1,500.0
Payments to retire long-term debt	(253.5)	(603.1)
Net change in commercial paper and other short-term borrowings	(91.6)	(278.4)
Other	(11.7)	10.9
Net cash flows from (used for) financing activities	526.1	587.4
Net increase (decrease) in cash, cash equivalents and restricted cash	174.2	213.9
Cash, cash equivalents and restricted cash at beginning of period	25.5	33.9
Cash, cash equivalents and restricted cash at end of period	199.7	247.8
Supplemental cash flows information:
Interest	(194.7)	(171.6)
Income taxes, net	0.8	(5.0)
Significant non-cash investing and financing activities:
Accrued capital expenditures	254.2	236.2
Beneficial interest obtained in exchange for securitized accounts receivable	237.0	243.7
IPL [Member]
Cash flows from operating activities:
Net income	247.1	232.6
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	243.4	209.2
Equity component of allowance for funds used during construction	(24.6)	(19.3)
Other	(13.2)	0.7
Other changes in assets and liabilities:
Accounts receivable	(365.0)	(353.2)
Accounts payable	(14.0)	(34.5)
Deferred income taxes	31.5	22.9
Other	33.3	(19.5)
Net cash flows from operating activities	138.5	38.9
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(696.3)	(635.2)
Cash receipts on sold receivables	255.9	337.2
Other	(43.7)	(30.9)
Net cash flows used for investing activities	(484.1)	(328.9)
Cash flows from (used for) financing activities:
Common stock dividends	(126.0)	(125.9)
Capital contributions from parent	100.0	230.0
Proceeds from issuance of long-term debt	600.0	500.0
Payments to retire long-term debt	0.0	(100.0)
Net change in commercial paper and other short-term borrowings	(50.4)	0.0
Other	(5.1)	15.0
Net cash flows from (used for) financing activities	518.5	519.1
Net increase (decrease) in cash, cash equivalents and restricted cash	172.9	229.1
Cash, cash equivalents and restricted cash at beginning of period	12.4	7.2
Cash, cash equivalents and restricted cash at end of period	185.3	236.3
Supplemental cash flows information:
Interest	(93.9)	(89.1)
Income taxes, net	8.2	(2.4)
Significant non-cash investing and financing activities:
Accrued capital expenditures	180.2	142.4
Beneficial interest obtained in exchange for securitized accounts receivable	237.0	243.7
WPL [Member]
Cash flows from operating activities:
Net income	183.2	170.1
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	176.6	164.2
Deferred tax expense and tax credits	54.6	50.3
Other	(7.8)	(12.0)
Other changes in assets and liabilities:
Accounts receivable	3.8	29.7
Regulatory liabilities	(28.6)	7.2
Other	(22.2)	(64.0)
Net cash flows from operating activities	359.6	345.5
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(307.6)	(445.0)
Other	(27.3)	(23.7)
Net cash flows used for investing activities	(334.9)	(468.7)
Cash flows from (used for) financing activities:
Common stock dividends	(107.9)	(105.0)
Capital contributions from parent	100.0	200.0
Proceeds from issuance of long-term debt	350.0	0.0
Payments to retire long-term debt	(250.0)	0.0
Net change in commercial paper and other short-term borrowings	(105.5)	13.4
Other	(10.9)	(1.7)
Net cash flows from (used for) financing activities	(24.3)	106.7
Net increase (decrease) in cash, cash equivalents and restricted cash	0.4	(16.5)
Cash, cash equivalents and restricted cash at beginning of period	9.2	24.2
Cash, cash equivalents and restricted cash at end of period	9.6	7.7
Supplemental cash flows information:
Interest	(73.9)	(68.5)
Income taxes, net	(7.0)	(11.2)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 70.3	$ 86.2

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Investments and Acquisitions

9 Months Ended

Sep. 30, 2019

Schedule of Investments [Line Items]

Investments and Acquisitions

INVESTMENTS AND ACQUISITIONS

Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):

	Three Months						Nine Months
	2019			2018			2019			2018
ATC Holdings		($10.5	)		($8.9	)		($30.0	)		($25.4	)
Non-utility wind farm in Oklahoma	(0.4		)	0.1			(2.8		)	(14.5		)
Other	(0.7		)	(1.0		)	(2.4		)	(1.7		)
		($11.6	)		($9.8	)		($35.2	)		($41.6	)

Non-utility Transportation Acquisitions - In the first quarter of 2019, Alliant Energy, through its wholly-owned non-utility subsidiaries, completed acquisitions of freight management companies located in Cedar Rapids, Iowa and Stoughton, Wisconsin. These acquisitions were purchased for $21 million, including contingent consideration of $8 million, which is expected to be paid within two years. The purchase price was largely allocated to intangibles and the remainder was allocated to working capital and property.

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Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 471.7	$ 153.3	$ 600.6	$ 446.5
Average amount outstanding (based on daily outstanding balances)	$ 399.5	$ 80.8	$ 476.3	$ 207.6
Weighted average interest rates	2.50%	2.20%	2.60%	2.10%
IPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 0.0	$ 0.0	$ 50.4	$ 31.4
Average amount outstanding (based on daily outstanding balances)	0.0	0.0	$ 0.2	$ 1.7
Weighted average interest rates			2.80%	2.30%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	89.7	75.4	$ 195.1	$ 109.4
Average amount outstanding (based on daily outstanding balances)	$ 27.0	$ 23.1	$ 101.8	$ 26.6
Weighted average interest rates	2.30%	2.00%	2.50%	1.90%

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Leases (Expected Maturities of Operating and Finance Lease Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	$ 0
Operating Leases Liability, 2020	2
Operating Leases Liability, 2021	2
Operating Leases Liability, 2022	2
Operating Leases Liability, 2023	2
Operating Leases Liability, Thereafter	13
Operating Leases Liability, Total	21
Operating Leases Liability, Less: amount representing interest	4
Operating Leases Liability, Present value of minimum lease payments	17
IPL [Member]
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	0
Operating Leases Liability, 2020	1
Operating Leases Liability, 2021	1
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, Thereafter	9
Operating Leases Liability, Total	13
Operating Leases Liability, Less: amount representing interest	3
Operating Leases Liability, Present value of minimum lease payments	10
WPL [Member]
Leases [Line Items]
Operating Leases Liability, Remainder of 2019	0
Operating Leases Liability, 2020	1
Operating Leases Liability, 2021	1
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, Thereafter	4
Operating Leases Liability, Total	8
Operating Leases Liability, Less: amount representing interest	1
Operating Leases Liability, Present value of minimum lease payments	7
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance Lease Liability, Remainder of 2019	4
Finance Lease Liability, 2020	15
Finance Lease Liability, 2021	15
Finance Lease Liability, 2022	15
Finance Lease Liability, 2023	15
Finance Lease Liability, Thereafter	20
Finance Lease Liability, Total	84
Finance Lease Liability, Less: amount representing interest	22
Finance Lease Liability, Present value of minimum lease payments	$ 62

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Related Parties (Amounts Billed Between Parties) (Details) - ATC [Member] - Equity Method Investee [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
ATC Billings To WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 28	$ 26	$ 82	$ 79
WPL Billings To ATC [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 3	$ 3	$ 10	$ 8

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Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 990.2	$ 928.6	$ 2,767.6	$ 2,661.0
Operating income (loss)	290.2	256.1	616.8	573.0
Net income attributable to common shareowners	226.0	205.5	445.7	426.8
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	596.5	547.6	1,592.8	1,548.2
Operating income (loss)	173.5	143.1	321.5	296.4
Net income attributable to common shareowners	141.1	126.5	239.4	224.9
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	372.1	370.7	1,113.4	1,083.2
Operating income (loss)	108.3	104.2	273.4	251.6
Net income attributable to common shareowners	75.5	76.3	183.2	170.1
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	915.9	861.2	2,350.5	2,296.2
Operating income (loss)	283.7	248.7	543.0	510.2
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	560.9	509.2	1,373.0	1,337.0
Operating income (loss)	175.1	144.7	290.8	275.7
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	355.0	352.0	977.5	959.2
Operating income (loss)	108.6	104.0	252.2	234.5
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	41.5	44.8	322.5	299.0
Operating income (loss)	(4.7)	(2.0)	47.7	34.9
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	24.8	26.7	187.8	177.0
Operating income (loss)	(4.2)	(3.1)	26.3	16.3
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	16.7	18.1	134.7	122.0
Operating income (loss)	(0.5)	1.1	21.4	18.6
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	11.2	12.3	33.2	36.2
Operating income (loss)	2.8	0.6	4.2	2.9
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	10.8	11.7	32.0	34.2
Operating income (loss)	2.6	1.5	4.4	4.4
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0.4	0.6	1.2	2.0
Operating income (loss)	0.2	(0.9)	(0.2)	(1.5)
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	968.6	918.3	2,706.2	2,631.4
Operating income (loss)	281.8	247.3	594.9	548.0
Net income attributable to common shareowners	216.6	202.8	422.6	395.0
Non-Utility [Member] | ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	21.6	10.3	61.4	29.6
Operating income (loss)	8.4	8.8	21.9	25.0
Net income attributable to common shareowners	$ 9.4	$ 2.7	$ 23.1	$ 31.8

XML

Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 21.7	$ 13.2	$ 12.2	$ 24.2	$ (10.7)	$ (12.2)
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	13.1		3.2
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	8.6		9.0
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	18.0	9.3	9.0	18.2	(4.1)	(1.4)
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	12.5		1.8
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	5.5		7.2
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3.7	$ 3.9	3.2	$ 6.0	$ (6.6)	$ (10.8)
WPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	0.6		1.4
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 3.1		$ 1.8

XML

Fair Value Measurements

9 Months Ended

Sep. 30, 2019

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

IPL [Member]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

WPL [Member]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$174.4		$174.4		$—		$—		$174.4		$—		$—		$—		$—		$—
Derivatives	30.3		—		8.1		22.2		30.3		28.3		—		8.9		19.4		28.3
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	31.8		—		31.3		0.5		31.8		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,191.9		—		7,016.4		2.0		7,018.4		5,502.8		—		5,858.4		2.4		5,860.8

IPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Money market fund investments		$173.7		$173.7		$—		$—		$173.7		$—		$—		$—		$—		$—
Derivatives	23.3		—		4.8		18.5		23.3		17.7		—		4.0		13.7		17.7
Deferred proceeds	237.0		—		—		237.0		237.0		119.4		—		—		119.4		119.4
Liabilities:
Derivatives	13.4		—		12.9		0.5		13.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,146.8		—		3,537.0		—		3,537.0		2,552.3		—		2,691.2		—		2,691.2

WPL	September 30, 2019										December 31, 2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$7.0		$—		$3.3		$3.7		$7.0		$10.6		$—		$4.9		$5.7		$10.6
Liabilities:
Derivatives	18.4		—		18.4		—		18.4		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.3		—		2,314.1		—		2,314.1		1,834.9		—		2,043.7		—		2,043.7

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$13.2			($10.7	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	12.7			25.7			—		—
Transfers out of Level 3	(1.2		)	15.6			—		—
Sales	—			(0.2		)	—		—
Settlements (a)	(3.0		)	(6.2		)	22.4		35.4
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$12.7			$26.1			$—		$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	6.9			15.7			—		—
Transfers out of Level 3	2.8			15.6			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.2		)	—		—
Settlements (a)	(13.8		)	(21.4		)	117.6		21.6
Ending balance, September 30		$21.7			$24.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.1			$16.5			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended September 30	2019			2018			2019		2018
Beginning balance, July 1		$9.3			($4.1	)		$214.6		$208.3
Total net gains included in changes in net assets (realized/unrealized)	11.5			16.8			—		—
Transfers out of Level 3	(0.6		)	10.5			—		—
Sales	—			(0.1		)	—		—
Settlements (a)	(2.2		)	(4.9		)	22.4		35.4
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$11.5			$16.8			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Nine Months Ended September 30	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.6			7.6			—		—
Transfers out of Level 3	2.0			10.5			—		—
Purchases	9.5			19.3			—		—
Sales	(0.1		)	(0.1		)	—		—
Settlements (a)	(11.0		)	(17.7		)	117.6		21.6
Ending balance, September 30		$18.0			$18.2			$237.0		$243.7
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$10.5			$7.9			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2019			2018
Beginning balance, July 1		$3.9			($6.6	)
Total net gains included in changes in net assets (realized/unrealized)	1.2			8.9
Transfers out of Level 3	(0.6		)	5.1
Sales	—			(0.1		)
Settlements	(0.8		)	(1.3		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30		$1.2			$9.3

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1.7		)	8.1
Transfers out of Level 3	0.8			5.1
Purchases	4.3			7.4
Sales	(0.1		)	(0.1		)
Settlements	(2.8		)	(3.7		)
Ending balance, September 30		$3.7			$6.0
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30		($0.4	)		$8.6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
September 30, 2019		$13.1		$8.6		$12.5		$5.5		$0.6		$3.1
December 31, 2018	3.2		9.0		1.8		7.2		1.4		1.8

XML

Common Equity

9 Months Ended

Sep. 30, 2019

Common Equity [Line Items]

Common Equity

COMMON EQUITY

Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2019	236,063,279
Equity forward agreements	3,790,300
Shareowner Direct Plan	390,630
Equity-based compensation plans	101,478
Other	(2,738	)
Shares outstanding, September 30, 2019	240,342,949

Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. The initial forward sale price of $44.33 per share is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreements. In 2019, Alliant Energy settled $167 million under the forward sale agreements by delivering 3,790,300 shares of newly issued Alliant Energy common stock at a weighted average forward sale price of $43.99 per share. Alliant Energy used the net proceeds from the settlements for general corporate purposes. As of September 30, 2019, 671,237 incremental shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements.

Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

Comprehensive Income - For the three and nine months ended September 30, 2019 and 2018, Alliant Energy’s other comprehensive income was not material; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three and nine months ended September 30, 2019 and 2018, IPL and WPL had no other comprehensive income; therefore, their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.

IPL [Member]

Common Equity [Line Items]

Common Equity

COMMON EQUITY

Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2019	236,063,279
Equity forward agreements	3,790,300
Shareowner Direct Plan	390,630
Equity-based compensation plans	101,478
Other	(2,738	)
Shares outstanding, September 30, 2019	240,342,949

Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. The initial forward sale price of $44.33 per share is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreements. In 2019, Alliant Energy settled $167 million under the forward sale agreements by delivering 3,790,300 shares of newly issued Alliant Energy common stock at a weighted average forward sale price of $43.99 per share. Alliant Energy used the net proceeds from the settlements for general corporate purposes. As of September 30, 2019, 671,237 incremental shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements.

Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

Comprehensive Income - For the three and nine months ended September 30, 2019 and 2018, Alliant Energy’s other comprehensive income was not material; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three and nine months ended September 30, 2019 and 2018, IPL and WPL had no other comprehensive income; therefore, their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.

WPL [Member]

Common Equity [Line Items]

Common Equity

COMMON EQUITY

Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2019	236,063,279
Equity forward agreements	3,790,300
Shareowner Direct Plan	390,630
Equity-based compensation plans	101,478
Other	(2,738	)
Shares outstanding, September 30, 2019	240,342,949

Equity Forward Agreements - In December 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. The initial forward sale price of $44.33 per share is subject to daily adjustment based on a floating interest rate factor, and will decrease by other fixed amounts specified in the forward sale agreements. In 2019, Alliant Energy settled $167 million under the forward sale agreements by delivering 3,790,300 shares of newly issued Alliant Energy common stock at a weighted average forward sale price of $43.99 per share. Alliant Energy used the net proceeds from the settlements for general corporate purposes. As of September 30, 2019, 671,237 incremental shares were included in the calculation of diluted EPS related to the remaining securities under the forward sale agreements.

Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

Comprehensive Income - For the three and nine months ended September 30, 2019 and 2018, Alliant Energy’s other comprehensive income was not material; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three and nine months ended September 30, 2019 and 2018, IPL and WPL had no other comprehensive income; therefore, their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.

XML

Income Taxes

9 Months Ended

Sep. 30, 2019

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

Deferred Tax Assets and Liabilities -

Carryforwards - At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

IPL [Member]

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

Deferred Tax Assets and Liabilities -

Carryforwards - At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

WPL [Member]

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income taxes by income before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.0		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.3	)	(5.4	)	(14.7	)	(5.5	)	(4.4	)	(6.4	)
Effect of rate-making on property-related differences	(5.6	)	(6.3	)	(9.0	)	(11.5	)	(2.8	)	(2.1	)
Amortization of excess deferred taxes	(1.1	)	(0.1	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(1.8	)	(5.7	)	1.3		(10.2	)	0.4		—
IPL’s tax benefit riders	(0.8	)	(2.3	)	(1.5	)	(4.8	)	—		—
Federal Tax Reform adjustments	—		(2.5	)	—		(0.9	)	—		(6.4	)
Other items, net	(0.2	)	(0.3	)	(0.3	)	(0.6	)	(0.2	)	(0.4	)
Overall income tax rate	9.2	%	5.3	%	4.6	%	(4.8	%)	18.5	%	11.8	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2019		2018		2019		2018		2019		2018
Statutory federal income tax rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefits	7.1		6.9		8.1		7.7		6.2		6.2
Production tax credits	(9.1	)	(5.4	)	(14.3	)	(5.4	)	(4.5	)	(6.6	)
Effect of rate-making on property-related differences	(5.7	)	(6.7	)	(9.3	)	(12.0	)	(2.6	)	(2.3	)
Amortization of excess deferred taxes	(1.1	)	(0.3	)	(0.3	)	—		(1.7	)	(0.1	)
Adjustment for prior period taxes	(0.7	)	(2.6	)	0.6		(5.4	)	(0.3	)	—
IPL’s tax benefit riders	(0.7	)	(2.2	)	(1.5	)	(4.6	)	—		—
Federal Tax Reform adjustments	—		(1.2	)	—		(0.5	)	—		(2.8	)
Other items, net	(1.0	)	(0.7	)	(0.1	)	(1.0	)	(0.4	)	(1.2	)
Overall income tax rate	9.8	%	8.8	%	4.2	%	(0.2	%)	17.7	%	14.2	%

Deferred Tax Assets and Liabilities -

Carryforwards - At September 30, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2031-2037		$611		$522		$41
State net operating losses	2019-2039	677		12		2
Federal tax credits	2022-2039	337		162		156

XML

Receivables

9 Months Ended

Sep. 30, 2019

Receivables [Line Items]

Receivables

RECEIVABLES

Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of September 30, 2019, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Maximum outstanding aggregate cash proceeds		$103.0		$110.0		$108.0		$116.0
Average outstanding aggregate cash proceeds	45.4		36.4		42.9		49.8

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

	September 30, 2019		December 31, 2018
Customer accounts receivable		$154.2		$140.1
Unbilled utility revenues	92.1		97.1
Other receivables	0.4		0.1
Receivables sold to third party	246.7		237.3
Less: cash proceeds	1.0		108.0
Deferred proceeds	245.7		129.3
Less: allowance for doubtful accounts	8.7		9.9
Fair value of deferred proceeds		$237.0		$119.4

As of September 30, 2019, outstanding receivables past due under the Receivables Agreement were $26.6 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Collections		$592.2		$549.5		$1,635.7		$1,550.2
Write-offs, net of recoveries	3.2		4.9		11.3		12.9

IPL [Member]

Receivables [Line Items]

Receivables

RECEIVABLES

Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of September 30, 2019, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Maximum outstanding aggregate cash proceeds		$103.0		$110.0		$108.0		$116.0
Average outstanding aggregate cash proceeds	45.4		36.4		42.9		49.8

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

	September 30, 2019		December 31, 2018
Customer accounts receivable		$154.2		$140.1
Unbilled utility revenues	92.1		97.1
Other receivables	0.4		0.1
Receivables sold to third party	246.7		237.3
Less: cash proceeds	1.0		108.0
Deferred proceeds	245.7		129.3
Less: allowance for doubtful accounts	8.7		9.9
Fair value of deferred proceeds		$237.0		$119.4

As of September 30, 2019, outstanding receivables past due under the Receivables Agreement were $26.6 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
Collections		$592.2		$549.5		$1,635.7		$1,550.2
Write-offs, net of recoveries	3.2		4.9		11.3		12.9

XML

Related Parties (Tables)

9 Months Ended

Sep. 30, 2019

Related Party Transactions [Line Items]

Services Provided, Sales Credited And Purchases

The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net Intercompany Payables

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

Related Amounts Billed Between Parties

The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
ATC billings to WPL		$28		$26		$82		$79
WPL billings to ATC	3		3		10		8

IPL [Member]

Related Party Transactions [Line Items]

Services Provided, Sales Credited And Purchases

The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net Intercompany Payables

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

WPL [Member]

Related Party Transactions [Line Items]

Services Provided, Sales Credited And Purchases

The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):

	IPL								WPL
	Three Months				Nine Months				Three Months				Nine Months
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate Services billings		$47		$43		$137		$128		$36		$33		$104		$100
Sales credited	23		11		50		34		2		7		6		16
Purchases billed	93		95		251		268		32		19		91		56

Net Intercompany Payables

Net intercompany payables to Corporate Services were as follows (in millions):

	IPL		WPL
	September 30, 2019	December 31, 2018	September 30, 2019	December 31, 2018
Net payables to Corporate Services	$108	$95	$75	$71

Related Amounts Billed Between Parties

The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):

	Three Months				Nine Months
	2019		2018		2019		2018
ATC billings to WPL		$28		$26		$82		$79
WPL billings to ATC	3		3		10		8

XML

Derivative Instruments (Tables)

9 Months Ended

Sep. 30, 2019

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Fair Value Of Financial Instruments

Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

IPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Fair Value Of Financial Instruments

Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

WPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of September 30, 2019, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	18,141	2019-2020	184,007	2019-2026	7,620	2019-2021	5,796	2019-2021
IPL	8,630	2019-2020	101,579	2019-2026	3,311	2019-2021	—	—
WPL	9,511	2019-2020	82,428	2019-2026	4,309	2019-2021	5,796	2019-2021

Fair Value Of Financial Instruments

Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Current derivative assets		$18.6		$24.6		$12.8		$16.1		$5.8		$8.5
Non-current derivative assets	11.7		3.7		10.5		1.6		1.2		2.1
Current derivative liabilities	13.4		5.6		5.6		3.1		7.8		2.5
Non-current derivative liabilities	18.4		17.7		7.8		8.1		10.6		9.6

XML

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	240,342,949	236,063,279
Shares in deferred compensation trust (in shares)	385,343	384,580
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 26.52	$ 25.60
IPL [Member]
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	24,000,000	24,000,000
Common stock, shares outstanding (in shares)	13,370,788	13,370,788
WPL [Member]
Common stock, par value (in dollars per share)	$ 5.00	$ 5.00
Common stock, shares authorized (in shares)	18,000,000	18,000,000
Common stock, shares outstanding (in shares)	13,236,601	13,236,601

XML

Debt (Credit Facilities) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt [Line Items]
Commercial paper outstanding	$ 349.6	$ 441.2
Commercial paper weighted average interest rates	2.30%
Available credit facility capacity	$ 650.4
IPL [Member]
Debt [Line Items]
Commercial paper outstanding	0.0	50.4
Available credit facility capacity	250.0
WPL [Member]
Debt [Line Items]
Commercial paper outstanding	0.0	$ 105.5
Available credit facility capacity	$ 300.0

XML

Leases (Finance Lease) (Details) - WPL [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Leases [Line Items]
Finance lease liabilities, Sheboygan Falls Energy Facility	$ 53.6	$ 53.6	$ 60.0
Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	34.0	34.0
Finance lease liabilities, Other current liabilities	8.0	8.0
Finance lease liabilities, Sheboygan Falls Energy Facility	54.0	54.0
Finance lease liabilities, Total	$ 62.0	$ 62.0
Finance Lease, Remaining lease term	6 years	6 years
Finance lease, Discount rate, percent	11.00%	11.00%
Finance lease, Depreciation expense	$ 1.0	$ 4.0
Finance lease, Interest expense	1.0	5.0
Finance lease, Total expense	$ 2.0	$ 9.0

XML

Related Parties (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
ATC [Member] | WPL Owed ATC LLC [Member] | Equity Method Investee [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 9	$ 8

XML

Commitments And Contingencies (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,230
Present value abandonment obligation	38
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	723
Indemnification obligations, maximum	17
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	498
Capital Purchase Obligation [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	124
Capital Purchase Obligation [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	79
Capital Purchase Obligation [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	45
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	145	[1]
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	144	[1]
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1	[1]
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Indemnification obligations, maximum	82
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Indemnification obligations, maximum	$ 17
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	54.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	60.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	82.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	27.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	82.00%

[1] Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.

XML

Investments and Acquisitions (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (11.6)	$ (9.8)	$ (35.2)	$ (41.6)
ATC Holdings [Member]
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(10.5)	(8.9)	(30.0)	(25.4)
Non-utility wind farm In Oklahoma [Member]
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(0.4)	0.1	(2.8)	(14.5)
Other [Member]
Schedule of Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (0.7)	$ (1.0)	$ (2.4)	$ (1.7)

XML

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Maximum [Member]
Receivables [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 103.0	$ 110.0	$ 108.0	$ 116.0
Average [Member]
Receivables [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 45.4	$ 36.4	$ 42.9	$ 49.8

XML

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets:
Money market fund investments	$ 174.4	$ 0.0
Deferred proceeds	237.0	119.4
Liabilities:
Long-term debt (incl. current maturities)	7,018.4	5,860.8
IPL [Member]
Assets:
Money market fund investments	173.7	0.0
Deferred proceeds	237.0	119.4
Liabilities:
Long-term debt (incl. current maturities)	3,537.0	2,691.2
WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,314.1	2,043.7
Commodity Contracts [Member]
Assets:
Derivatives	30.3	28.3
Liabilities:
Derivatives	31.8	23.3
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	23.3	17.7
Liabilities:
Derivatives	13.4	11.2
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	7.0	10.6
Liabilities:
Derivatives	18.4	12.1
Level 1 [Member]
Assets:
Money market fund investments	174.4	0.0
Deferred proceeds	0.0	0.0
Liabilities:
Long-term debt (incl. current maturities)	0.0	0.0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	173.7	0.0
Deferred proceeds	0.0	0.0
Liabilities:
Long-term debt (incl. current maturities)	0.0	0.0
Level 1 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0.0	0.0
Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0.0	0.0
Liabilities:
Derivatives	0.0	0.0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	0.0	0.0
Liabilities:
Derivatives	0.0	0.0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	0.0	0.0
Liabilities:
Derivatives	0.0	0.0
Level 2 [Member]
Assets:
Money market fund investments	0.0	0.0
Deferred proceeds	0.0	0.0
Liabilities:
Long-term debt (incl. current maturities)	7,016.4	5,858.4
Level 2 [Member] | IPL [Member]
Assets:
Money market fund investments	0.0	0.0
Deferred proceeds	0.0	0.0
Liabilities:
Long-term debt (incl. current maturities)	3,537.0	2,691.2
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,314.1	2,043.7
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	8.1	8.9
Liabilities:
Derivatives	31.3	16.1
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	4.8	4.0
Liabilities:
Derivatives	12.9	6.5
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	3.3	4.9
Liabilities:
Derivatives	18.4	9.6
Level 3 [Member]
Assets:
Money market fund investments	0.0	0.0
Deferred proceeds	237.0	119.4
Liabilities:
Long-term debt (incl. current maturities)	2.0	2.4
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0.0	0.0
Deferred proceeds	237.0	119.4
Liabilities:
Long-term debt (incl. current maturities)	0.0	0.0
Level 3 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0.0	0.0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	22.2	19.4
Liabilities:
Derivatives	0.5	7.2
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	18.5	13.7
Liabilities:
Derivatives	0.5	4.7
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	3.7	5.7
Liabilities:
Derivatives	0.0	2.5
Carrying Amount [Member]
Assets:
Money market fund investments	174.4	0.0
Deferred proceeds	237.0	119.4
Liabilities:
Long-term debt (incl. current maturities)	6,191.9	5,502.8
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	173.7	0.0
Deferred proceeds	237.0	119.4
Liabilities:
Long-term debt (incl. current maturities)	3,146.8	2,552.3
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	1,932.3	1,834.9
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	30.3	28.3
Liabilities:
Derivatives	31.8	23.3
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	23.3	17.7
Liabilities:
Derivatives	13.4	11.2
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	7.0	10.6
Liabilities:
Derivatives	$ 18.4	$ 12.1

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Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	7.00%	6.90%	7.10%	6.90%
Production tax credits	(9.30%)	(5.40%)	(9.10%)	(5.40%)
Effect of rate-making on property-related differences	(5.60%)	(6.30%)	(5.70%)	(6.70%)
Amortization of excess deferred taxes	(1.10%)	(0.10%)	(1.10%)	(0.30%)
Adjustment for prior period taxes	(1.80%)	(5.70%)	(0.70%)	(2.60%)
IPL's tax benefit riders	(0.80%)	(2.30%)	(0.70%)	(2.20%)
Federal Tax Reform adjustments	0.00%	(2.50%)	0.00%	(1.20%)
Other items, net	(0.20%)	(0.30%)	(1.00%)	(0.70%)
Overall income tax rate	9.20%	5.30%	9.80%	8.80%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	8.10%	7.70%	8.10%	7.70%
Production tax credits	(14.70%)	(5.50%)	(14.30%)	(5.40%)
Effect of rate-making on property-related differences	(9.00%)	(11.50%)	(9.30%)	(12.00%)
Amortization of excess deferred taxes	(0.30%)	0.00%	(0.30%)	0.00%
Adjustment for prior period taxes	1.30%	(10.20%)	0.60%	(5.40%)
IPL's tax benefit riders	(1.50%)	(4.80%)	(1.50%)	(4.60%)
Federal Tax Reform adjustments	0.00%	(0.90%)	0.00%	(0.50%)
Other items, net	(0.30%)	(0.60%)	(0.10%)	(1.00%)
Overall income tax rate	4.60%	(4.80%)	4.20%	(0.20%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	6.20%	6.20%	6.20%	6.20%
Production tax credits	(4.40%)	(6.40%)	(4.50%)	(6.60%)
Effect of rate-making on property-related differences	(2.80%)	(2.10%)	(2.60%)	(2.30%)
Amortization of excess deferred taxes	(1.70%)	(0.10%)	(1.70%)	(0.10%)
Adjustment for prior period taxes	0.40%	0.00%	(0.30%)	0.00%
Federal Tax Reform adjustments	0.00%	(6.40%)	0.00%	(2.80%)
Other items, net	(0.20%)	(0.40%)	(0.40%)	(1.20%)
Overall income tax rate	18.50%	11.80%	17.70%	14.20%

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Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Compensation expense	$ 7.5	$ 4.2	$ 15.6	$ 12.6
Income tax benefits	2.1	1.2	4.4	3.6
IPL [Member]
Compensation expense	4.2	2.4	8.7	7.0
Income tax benefits	1.2	0.7	2.5	2.1
WPL [Member]
Compensation expense	3.0	1.7	6.2	5.1
Income tax benefits	$ 0.8	$ 0.5	$ 1.7	$ 1.4

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Summary Of Significant Accounting Policies (Policy)

9 Months Ended

Sep. 30, 2019

General, Basis of Accounting

The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

General, Use of Estimates

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred.

General, Reclassification

Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

Cash and Cash Equivalents

Cash and Cash Equivalents - At September 30, 2019, Alliant Energy’s and IPL’s cash and cash equivalents included $174.4 million and $173.7 million of money market fund investments, with interest rates of 2.0% and 2.0%, respectively.

Leases

Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

New Accounting Standards

New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

IPL [Member]

General, Basis of Accounting

The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

General, Use of Estimates

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred.

General, Reclassification

Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

Cash and Cash Equivalents

Cash and Cash Equivalents - At September 30, 2019, Alliant Energy’s and IPL’s cash and cash equivalents included $174.4 million and $173.7 million of money market fund investments, with interest rates of 2.0% and 2.0%, respectively.

Leases

Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

New Accounting Standards

New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

WPL [Member]

General, Basis of Accounting

The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the latest combined Annual Report on Form 10-K.

General, Use of Estimates

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the nine months ended September 30, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred.

General, Reclassification

Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

Leases

Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and interest expenses. Finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

New Accounting Standards

New Accounting Standards -

Credit Losses - In June 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables and certain other assets. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 using the modified retrospective method of adoption, which requires cumulative effect adjustments to retained earnings on January 1, 2020 upon adoption. Alliant Energy, IPL and WPL will continue to evaluate the impact of this standard and do not currently expect a material change to their financial condition or results of operations as a result of adopting this standard.

Cloud Computing Arrangements - In August 2018, the Financial Accounting Standards Board issued an accounting standard that clarifies capitalization and presentation requirements of implementation costs incurred in cloud computing arrangements. Alliant Energy, IPL and WPL will adopt this standard on January 1, 2020 and are currently evaluating the impact of this standard on their financial statements.

Leases - In February 2016, the Financial Accounting Standards Board issued an accounting standard requiring lease assets and lease liabilities, including operating leases, to be recognized on the balance sheet. The accounting for capital leases, now referred to as finance leases, remains unchanged with the adoption of this standard. Alliant Energy, IPL and WPL adopted this standard on January 1, 2019 using an optional transition approach and there was no cumulative effect adjustment to the balance sheets as of January 1, 2019. Prior period amounts have not been restated to reflect the adoption of this standard and continue to be reported under the accounting standards in effect for those periods. Upon transition to the new standard, Alliant Energy, IPL and WPL elected the land easement transition practical expedient, for which existing land easements that were not previously accounted for as leases under the original accounting standards did not need to be evaluated under the new accounting standard. In addition, Alliant Energy, IPL and WPL evaluated land easements that were previously accounted for as leases and determined that the majority of these land easements relate to joint-use land sites, and do not meet the criteria for leases under the new accounting standard. Therefore, these land easement arrangements are no longer reflected as operating leases effective January 1, 2019. Refer to Note 7 for further discussion of leases.

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Common Equity (Tables)

9 Months Ended

Sep. 30, 2019

Schedule of Capitalization, Equity [Line Items]

Common Share Activity

A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2019	236,063,279
Equity forward agreements	3,790,300
Shareowner Direct Plan	390,630
Equity-based compensation plans	101,478
Other	(2,738	)
Shares outstanding, September 30, 2019	240,342,949

Changes in Shareowners' Equity

A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

IPL [Member]

Schedule of Capitalization, Equity [Line Items]

Changes in Shareowners' Equity

A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL [Member]

Schedule of Capitalization, Equity [Line Items]

Changes in Shareowners' Equity

A summary of changes in shareowners’ equity was as follows (in millions):

Alliant Energy	Total Alliant Energy Common Equity
									Accumulated			Shares in			Cumulative
			Additional						Other			Deferred			Preferred
	Common		Paid-In			Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital			Earnings			Income (Loss)			Trust			of IPL		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$2.4		$2,108.4			$2,597.8			$1.0			($10.0	)		$200.0		$4,899.6
Net income attributable to Alliant Energy common shareowners						226.0											226.0
Common stock dividends ($0.355 per share)						(84.7		)									(84.7		)
Equity forward settlements and Shareowner Direct Plan issuances			124.8														124.8
Equity-based compensation plans and other			3.7									(0.2		)			3.5
Ending balance, September 30		$2.4		$2,236.9			$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Three Months Ended September 30, 2018
Beginning balance, July 1		$2.3		$1,947.2			$2,412.5			$0.1			($11.4	)		$200.0		$4,550.7
Net income attributable to Alliant Energy common shareowners						205.5											205.5
Common stock dividends ($0.335 per share)						(78.5		)									(78.5		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		91.1														91.2
Equity-based compensation plans and other			(0.1		)							1.9					1.8
Other comprehensive loss, net of tax									(0.3		)						(0.3		)
Ending balance, September 30		$2.4		$2,038.2			$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

Alliant Energy	Total Alliant Energy Common Equity
								Accumulated			Shares in			Cumulative
			Additional					Other			Deferred			Preferred
	Common		Paid-In		Retained			Comprehensive			Compensation			Stock		Total
	Stock		Capital		Earnings			Income (Loss)			Trust			of IPL		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$2.4		$2,045.5		$2,545.9			$1.7			($9.8	)		$200.0		$4,785.7
Net income attributable to Alliant Energy common shareowners					445.7											445.7
Common stock dividends ($1.065 per share)					(252.5		)									(252.5		)
Equity forward settlements and Shareowner Direct Plan issuances			185.4													185.4
Equity-based compensation plans and other			6.0								(0.4		)			5.6
Other comprehensive loss, net of tax								(0.7		)						(0.7		)
Ending balance, September 30		$2.4		$2,236.9		$2,739.1			$1.0			($10.2	)		$200.0		$5,169.2
Nine Months Ended September 30, 2018
Beginning balance, January 1		$2.3		$1,845.5		$2,346.0			($0.5	)		($11.1	)		$200.0		$4,382.2
Net income attributable to Alliant Energy common shareowners					426.8											426.8
Common stock dividends ($1.005 per share)					(233.3		)									(233.3		)
At-the-market offering program and Shareowner Direct Plan issuances	0.1		191.2													191.3
Equity-based compensation plans and other			1.5								1.6					3.1
Other comprehensive income, net of tax								0.3								0.3
Ending balance, September 30		$2.4		$2,038.2		$2,539.5			($0.2	)		($9.5	)		$200.0		$4,770.4

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$33.4		$2,322.8		$788.9			$200.0		$3,345.1
Earnings available for common stock					141.1					141.1
Common stock dividends					(42.1		)			(42.1		)
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Three Months Ended September 30, 2018
Beginning balance, July 1		$33.4		$1,927.8		$692.9			$200.0		$2,854.1
Earnings available for common stock					126.5					126.5
Common stock dividends					(41.9		)			(41.9		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

IPL	Total IPL Common Equity
			Additional					Cumulative
	Common		Paid-In		Retained			Preferred		Total
	Stock		Capital		Earnings			Stock		Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$33.4		$2,222.8		$774.5			$200.0		$3,230.7
Earnings available for common stock					239.4					239.4
Common stock dividends					(126.0		)			(126.0		)
Capital contributions from parent			100.0							100.0
Ending balance, September 30		$33.4		$2,322.8		$887.9			$200.0		$3,444.1
Nine Months Ended September 30, 2018
Beginning balance, January 1		$33.4		$1,797.8		$678.5			$200.0		$2,709.7
Earnings available for common stock					224.9					224.9
Common stock dividends					(125.9		)			(125.9		)
Capital contributions from parent			230.0							230.0
Ending balance, September 30		$33.4		$2,027.8		$777.5			$200.0		$3,038.7

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Three Months Ended September 30, 2019
Beginning balance, July 1		$66.2		$1,309.0		$810.0			$2,185.2
Earnings available for common stock					75.5			75.5
Common stock dividends					(35.9		)	(35.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Three Months Ended September 30, 2018
Beginning balance, July 1		$66.2		$1,259.0		$730.0			$2,055.2
Earnings available for common stock					76.3			76.3
Common stock dividends					(34.9		)	(34.9		)
Capital contributions from parent			50.0					50.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6

WPL			Additional					Total
	Common		Paid-In		Retained			Common
	Stock		Capital		Earnings			Equity
Nine Months Ended September 30, 2019
Beginning balance, January 1		$66.2		$1,309.0		$774.3			$2,149.5
Earnings available for common stock					183.2			183.2
Common stock dividends					(107.9		)	(107.9		)
Capital contributions from parent			100.0					100.0
Ending balance, September 30		$66.2		$1,409.0		$849.6			$2,324.8
Nine Months Ended September 30, 2018
Beginning balance, January 1		$66.2		$1,109.0		$706.3			$1,881.5
Earnings available for common stock					170.1			170.1
Common stock dividends					(105.0		)	(105.0		)
Capital contributions from parent			200.0					200.0
Ending balance, September 30		$66.2		$1,309.0		$771.4			$2,146.6