Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 381.7	$ 388.4		$ 393.3
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	411.6	401.3		388.1
Other amortizations	(4.8)	12.4		54.2
Deferred tax expense (benefit) and tax credits	84.6	114.2		55.2
Equity (income) loss from unconsolidated investments, net	(39.6)	(33.8)		(40.4)
Distributions from equity method investments	28.3	30.6		36.4
Equity component of allowance for funds used during construction	(42.3)	(24.4)		(23.1)
Asset valuation charges for Franklin County wind farm	86.4	0.0		0.0
Other	0.8	15.7		2.0
Other changes in assets and liabilities:
Accounts receivable	(121.4)	36.8		48.7
Sales of accounts receivable	16.0	(17.0)		(7.0)
Regulatory assets	(3.6)	(104.5)		(439.8)
Regulatory liabilities	(63.0)	(67.8)		10.8
Deferred income taxes	102.4	94.6		138.4
Pension and other benefit obligations	38.1	30.1		215.1
Other	(15.6)	(5.4)		59.7
Net cash flows from operating activities	859.6	871.2		891.6
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(1,142.7)	(963.6)		(838.9)
Alliant Energy Corporate Services, Inc. and non-regulated businesses construction and acquisition expenditures	(54.1)	(70.7)		(63.9)
Proceeds from Minnesota electric and natural gas distribution asset sales	0.0	139.9		0.0
Other	10.3	(24.8)		(14.9)
Net cash flows from (used for) investing activities	(1,186.5)	(919.2)		(917.7)
Cash flows from (used for) financing activities:
Common stock dividends	(266.5)	(247.3)		(225.8)
Proceeds from issuance of common stock, net	26.6	151.2	[1]	0.0
Proceeds from issuance of long-term debt	800.0	250.7		812.9
Payments to retire long-term debt	(313.4)	(183.0)		(358.5)
Net change in commercial paper	84.3	18.5		(138.1)
Other	(1.7)	6.8		(17.3)
Net cash flows from (used for) financing activities	329.3	(3.1)		73.2
Net increase (decrease) in cash and cash equivalents	2.4	(51.1)		47.1
Cash and cash equivalents at beginning of period	5.8	56.9		9.8
Cash and cash equivalents at end of period	8.2	5.8		56.9
Supplemental cash flows information:
Interest, net of capitalized interest	(192.4)	(184.8)		(180.8)
Income taxes, net	(9.8)	0.0		5.3
Significant non-cash investing and financing activities:
Accrued capital expenditures	154.4	148.3		160.3
IPL [Member]
Cash flows from operating activities:
Net income	225.8	196.2		191.8
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	210.8	207.2		197.5
Deferred tax expense (benefit) and tax credits	35.6	28.9		(11.5)
Equity component of allowance for funds used during construction	(35.2)	(18.6)		(17.1)
Other	2.9	19.5		11.3
Other changes in assets and liabilities:
Accounts receivable	(59.7)	20.4		43.3
Sales of accounts receivable	16.0	(17.0)		(7.0)
Regulatory assets	(54.7)	(76.3)		(272.9)
Accounts payable	8.0	(42.7)		18.8
Regulatory liabilities	(67.3)	(75.5)		(18.9)
Deferred income taxes	97.7	82.1		140.4
Pension and other benefit obligations	13.1	17.8		93.8
Other	(31.1)	43.0		36.6
Net cash flows from operating activities	361.9	385.0		406.1
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(689.7)	(619.3)		(526.0)
Proceeds from Minnesota electric and natural gas distribution asset sales	0.0	139.9		0.0
Other	(3.9)	(32.5)		(26.7)
Net cash flows from (used for) investing activities	(693.6)	(511.9)		(552.7)
Cash flows from (used for) financing activities:
Common stock dividends	(151.9)	(140.0)		(140.0)
Capital contributions from parent	190.0	165.0		90.0
Proceeds from issuance of long-term debt	300.0	250.0		250.0
Payments to retire long-term debt	0.0	(150.0)		(38.4)
Other	(7.6)	1.1		(14.1)
Net cash flows from (used for) financing activities	330.5	126.1		147.5
Net increase (decrease) in cash and cash equivalents	(1.2)	(0.8)		0.9
Cash and cash equivalents at beginning of period	4.5	5.3		4.4
Cash and cash equivalents at end of period	3.3	4.5		5.3
Supplemental cash flows information:
Interest, net of capitalized interest	(99.7)	(93.9)		(89.8)
Income taxes, net	(11.1)	19.3		20.1
Significant non-cash investing and financing activities:
Accrued capital expenditures	53.8	77.0		113.2
WPL [Member]
Cash flows from operating activities:
Net income	192.8	177.6		181.1
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	192.5	184.3		181.2
Other amortizations	(8.7)	5.3		47.3
Deferred tax expense (benefit) and tax credits	114.5	77.6		82.6
Equity (income) loss from unconsolidated investments, net	(39.8)	(35.1)		(42.8)
Distributions from equity method investments	28.3	30.6		36.4
Other	(6.3)	(5.7)		(7.2)
Other changes in assets and liabilities:
Accounts receivable	(47.6)	3.7		2.2
Regulatory assets	51.1	(28.2)		(166.9)
Pension and other benefit obligations	19.1	8.3		92.0
Other	25.5	31.4		18.5
Net cash flows from operating activities	521.4	449.8		424.4
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(453.0)	(344.3)		(312.9)
Other	(25.9)	(13.9)		(7.2)
Net cash flows from (used for) investing activities	(478.9)	(358.2)		(320.1)
Cash flows from (used for) financing activities:
Common stock dividends	(135.0)	(126.9)		(118.7)
Capital contributions from parent	60.0	0.0		0.0
Proceeds from issuance of long-term debt	0.0	0.0		250.0
Net change in commercial paper	32.4	19.9		(183.7)
Other	3.9	(30.9)		(5.7)
Net cash flows from (used for) financing activities	(38.7)	(137.9)		(58.1)
Net increase (decrease) in cash and cash equivalents	3.8	(46.3)		46.2
Cash and cash equivalents at beginning of period	0.4	46.7		0.5
Cash and cash equivalents at end of period	4.2	0.4		46.7
Supplemental cash flows information:
Interest, net of capitalized interest	(91.5)	(93.1)		(84.6)
Income taxes, net	27.8	(7.4)		(12.2)
Significant non-cash investing and financing activities:
Accrued capital expenditures	93.1	55.2		38.4
Transfer of investment in ATC and tax liability to ATI	$ (163.6)	$ 0.0		$ 0.0

[1] Amounts reflect the effects of a two-for-one common stock split distributed in May 2016.