Segments Of Business (Tables)

12 Months Ended

Dec. 31, 2017

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 Investment,
	Utility											Non-utility,			Alliant Energy
2017	Electric			Gas		Other			Total			Parent and Other			Consolidated
Operating 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)	586.5			45.3		(11.7		)	620.1			33.3			653.4
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 Investment,
	Utility											Non-utility,			Alliant Energy
2016	Electric			Gas		Other			Total			Parent and Other			Consolidated
Operating 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)	571.9			30.7		(4.8		)	597.8			(60.8		)	537.0
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

											ATC Investment,
	Utility										Non-utility,			Alliant Energy
2015	Electric			Gas		Other		Total			Parent and Other			Consolidated
Operating revenues		$2,770.5			$381.2		$57.9		$3,209.6			$44.0			$3,253.6
Depreciation and amortization	358.6			31.1		1.8		391.5			9.8			401.3
Operating income	514.1			34.6		1.9		550.6			26.4			577.0
Interest expense								189.2			(2.1		)	187.1
Equity income from unconsolidated investments, net	(0.9		)	—		—		(0.9		)	(32.9		)	(33.8		)
Income taxes								46.2			24.2			70.4
Net income attributable to Alliant Energy common shareowners								343.4			34.8			378.2
Total assets	9,918.0			939.3		828.9		11,686.2			809.0			12,495.2
Investments in equity method subsidiaries	8.7			—		—		8.7			294.2			302.9
Construction and acquisition expenditures	852.5			106.4		1.4		960.3			74.0			1,034.3

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):

2017	Electric		Gas		Other			Total
Operating 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)	281.1		20.8		(5.0		)	296.9
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
Operating revenues		$1,569.7		$204.0		$46.7		$1,820.4
Depreciation and amortization	189.4		19.3		2.1		210.8
Operating income	252.0		15.5		3.3		270.8
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

2015	Electric		Gas		Other		Total
Operating revenues		$1,503.8		$217.3		$53.4		$1,774.5
Depreciation and amortization	187.9		17.5		1.8		207.2
Operating income	218.8		17.7		5.4		241.9
Interest expense							96.8
Income tax benefit							(22.7		)
Earnings available for common stock							186.0
Total assets	5,754.1		548.2		406.8		6,709.1
Construction and acquisition expenditures	561.2		56.7		1.4		619.3

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):

2017	Electric			Gas		Other			Total
Operating revenues		$1,295.8			$174.9		$2.1			$1,472.8
Depreciation and amortization	196.9			16.0		—			212.9
Operating income (loss)	305.4			24.5		(6.7		)	323.2
Interest expense									93.8
Equity income from unconsolidated investments	(0.7		)	—		—			(0.7		)
Income taxes									61.9
Earnings available for common stock									186.6
Total assets	4,871.8			471.9		412.8			5,756.5
Investments in equity method subsidiaries	8.3			—		—			8.3
Construction and acquisition expenditures	592.4			44.5		0.5			637.4

2016	Electric			Gas		Other			Total
Operating revenues		$1,305.8			$151.4		$1.9			$1,459.1
Depreciation and amortization	177.6			14.9		—			192.5
Operating income (loss)	319.9			15.2		(8.1		)	327.0
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
Investments in equity method subsidiaries	7.7			—		—			7.7
Construction and acquisition expenditures	395.9			45.6		11.5			453.0

2015	Electric			Gas		Other			Total
Operating revenues		$1,266.7			$163.9		$4.5			$1,435.1
Depreciation and amortization	170.7			13.6		—			184.3
Operating income (loss)	295.3			16.9		(3.5		)	308.7
Interest expense									92.4
Equity income from unconsolidated investments	(0.9		)	—		(34.2		)	(35.1		)
Income taxes									82.9
Earnings available for common stock									176.3
Total assets	4,163.9			391.1		715.4			5,270.4
Investments in equity method subsidiaries	8.7			—		293.3			302.0
Construction and acquisition expenditures	291.3			49.7		3.3			344.3