Segments Of Business (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting Information [Line Items]

Schedule of Segments of Business

Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):

											ATC Holdings,
	Utility										Non-utility,			Alliant Energy
2018	Electric			Gas		Other		Total			Parent and Other			Consolidated
Revenues		$3,000.3			$446.6		$48.0		$3,494.9			$39.6			$3,534.5
Depreciation and amortization	457.3			42.0		3.6		502.9			4.0			506.9
Operating income	610.2			53.2		0.3		663.7			30.7			694.4
Interest expense								217.2			29.8			247.0
Equity income from unconsolidated investments, net	(0.9		)	—		—		(0.9		)	(53.7		)	(54.6		)
Income taxes								33.0			14.7			47.7
Net income attributable to Alliant Energy common shareowners								472.1			40.0			512.1
Total assets	12,486.3			1,184.4		893.2		14,563.9			862.1			15,426.0
Investments in equity method subsidiaries	8.1			—		—		8.1			413.2			421.3
Construction and acquisition expenditures	1,421.1			146.8		0.4		1,568.3			65.6			1,633.9

												ATC Holdings,
	Utility											Non-utility,			Alliant Energy
2017	Electric			Gas		Other			Total			Parent and Other			Consolidated
Revenues		$2,894.7			$400.9		$47.5			$3,343.1			$39.1			$3,382.2
Depreciation and amortization	412.0			38.2		7.7			457.9			3.9			461.8
Operating income (loss)	601.7			47.7		(11.6		)	637.8			33.4			671.2
Interest expense									206.2			9.4			215.6
Equity income from unconsolidated investments, net	(0.7		)	—		—			(0.7		)	(44.1		)	(44.8		)
Income taxes									51.0			15.7			66.7
Net income attributable to Alliant Energy common shareowners									403.4			53.9			457.3
Total assets	11,396.2			1,199.8		766.5			13,362.5			825.3			14,187.8
Investments in equity method subsidiaries	8.3			—		—			8.3			373.1			381.4
Construction and acquisition expenditures	1,154.9			125.2		1.7			1,281.8			185.1			1,466.9

												ATC Holdings,
	Utility											Non-utility,			Alliant Energy
2016	Electric			Gas		Other			Total			Parent and Other			Consolidated
Revenues		$2,875.5			$355.4		$48.6			$3,279.5			$40.5			$3,320.0
Depreciation and amortization	367.0			34.2		2.1			403.3			8.3			411.6
Operating income (loss)	586.5			33.0		(4.7		)	614.8			(60.7		)	554.1
Interest expense									194.6			1.6			196.2
Equity income from unconsolidated investments, net	(0.7		)	—		—			(0.7		)	(38.9		)	(39.6		)
Income tax expense (benefit)									71.4			(12.0		)	59.4
Net income (loss) attributable to Alliant Energy common shareowners									385.2			(13.7		)	371.5
Total assets	10,722.9			1,091.1		781.0			12,595.0			778.8			13,373.8
Investments in equity method subsidiaries	7.7			—		—			7.7			318.3			326.0
Construction and acquisition expenditures	994.0			137.1		0.1			1,131.2			65.6			1,196.8

IPL [Member]

Segment Reporting Information [Line Items]

Schedule of Segments of Business

Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):

2018	Electric		Gas		Other		Total
Revenues		$1,731.1		$266.2		$45.0		$2,042.3
Depreciation and amortization	254.7		25.2		3.6		283.5
Operating income	318.2		28.3		4.3		350.8
Interest expense							119.4
Income tax benefit							(3.2		)
Earnings available for common stock							264.0
Total assets	7,219.9		687.5		504.0		8,411.4
Construction and acquisition expenditures	890.6		99.7		0.4		990.7

2017	Electric		Gas		Other			Total
Revenues		$1,598.9		$226.0		$45.4			$1,870.3
Depreciation and amortization	215.1		22.2		7.7			245.0
Operating income (loss)	287.3		21.7		(4.9		)	304.1
Interest expense								112.4
Income tax benefit								(10.9		)
Earnings available for common stock								216.8
Total assets	6,524.4		727.9		353.7			7,606.0
Construction and acquisition expenditures	594.1		80.7		1.2			676.0

2016	Electric		Gas		Other		Total
Revenues		$1,569.7		$204.0		$46.7		$1,820.4
Depreciation and amortization	189.4		19.3		2.1		210.8
Operating income	257.8		16.4		3.4		277.6
Interest expense							103.2
Income tax benefit							(5.9		)
Earnings available for common stock							215.6
Total assets	6,278.2		653.3		373.2		7,304.7
Construction and acquisition expenditures	598.1		91.5		0.1		689.7

WPL [Member]

Segment Reporting Information [Line Items]

Schedule of Segments of Business

Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):

2018	Electric		Gas		Other			Total
Revenues		$1,269.2		$180.4		$3.0			$1,452.6
Depreciation and amortization	202.6		16.8		—			219.4
Operating income (loss)	292.0		24.9		(4.0		)	312.9
Interest expense								97.8
Income taxes								36.2
Earnings available for common stock								208.1
Total assets	5,266.4		496.9		389.2			6,152.5
Construction and acquisition expenditures	530.5		47.1		—			577.6

2017	Electric		Gas		Other			Total
Revenues		$1,295.8		$174.9		$2.1			$1,472.8
Depreciation and amortization	196.9		16.0		—			212.9
Operating income (loss)	314.4		26.0		(6.7		)	333.7
Interest expense								93.8
Income taxes								61.9
Earnings available for common stock								186.6
Total assets	4,871.8		471.9		412.8			5,756.5
Construction and acquisition expenditures	592.4		44.5		0.5			637.4

2016	Electric			Gas		Other			Total
Revenues		$1,305.8			$151.4		$1.9			$1,459.1
Depreciation and amortization	177.6			14.9		—			192.5
Operating income (loss)	328.7			16.6		(8.1		)	337.2
Interest expense									91.4
Equity income from unconsolidated investments	(0.7		)	—		(39.1		)	(39.8		)
Income taxes									93.3
Earnings available for common stock									190.4
Total assets	4,444.7			437.8		407.8			5,290.3
Construction and acquisition expenditures	395.9			45.6		11.5			453.0