Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Utility:
Electric	$ 640.4	$ 643.9	$ 1,311.7	$ 1,319.7
Gas	51.7	76.9	250.1	317.6
Other	14.8	15.6	31.2	38.4
Non-regulated	10.3	13.9	21.6	27.4
Total operating revenues	717.2	750.3	1,614.6	1,703.1
Utility:
Electric production fuel and purchased power	185.2	214.1	401.1	452.8
Electric transmission service	116.9	105.5	240.1	219.6
Cost of gas sold	21.9	45.0	152.7	206.9
Other operation and maintenance	157.3	160.7	303.9	321.7
Non-regulated operation and maintenance	0.0	1.8	1.3	3.1
Depreciation and amortization	100.4	95.8	200.6	191.3
Taxes other than income taxes	26.5	24.1	53.0	50.2
Total operating expenses	608.2	647.0	1,352.7	1,445.6
Operating income	109.0	103.3	261.9	257.5
Interest expense and other:
Interest expense	46.5	45.1	93.1	90.3
Equity income from unconsolidated investments, net	(11.3)	(11.3)	(17.8)	(22.7)
Allowance for funds used during construction	(8.6)	(8.4)	(15.4)	(17.5)
Interest income and other	(0.2)	0.1	(0.3)	(1.6)
Total interest expense and other	26.4	25.5	59.6	48.5
Income from continuing operations before income taxes	82.6	77.8	202.3	209.0
Income tax expense (benefit)	11.2	13.2	31.7	33.8
Income from continuing operations, net of tax	71.4	64.6	170.6	175.2
Loss from discontinued operations, net of tax	(1.3)	(0.3)	(1.3)	(0.3)
Net income (loss)	70.1	64.3	169.3	174.9
Preferred dividend requirements of IPL	2.5	2.5	5.1	5.1
Net income (loss) attributable to common shareowners	$ 67.6	$ 61.8	$ 164.2	$ 169.8
Weighted average number of common shares outstanding (basic and diluted) (in shares)	113.1	110.8	112.1	110.8
Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic and diluted):
Income from continuing operations, net of tax (in dollars per share)	$ 0.61	$ 0.56	$ 1.47	$ 1.53
Loss from discontinued operations, net of tax (in dollars per share)	(0.01)	0.00	(0.01)	0.00
Net income (in dollars per share)	$ 0.60	$ 0.56	$ 1.46	$ 1.53
Amounts attributable to common shareowners:
Income from continuing operations, net of tax	$ 68.9	$ 62.1	$ 165.5	$ 170.1
Loss from discontinued operations, net of tax	(1.3)	(0.3)	(1.3)	(0.3)
Net income (loss) attributable to common shareowners	$ 67.6	$ 61.8	$ 164.2	$ 169.8
Dividends declared per common share (in dollars per share)	$ 0.55	$ 0.51	$ 1.10	$ 1.02
IPL [Member]
Utility:
Electric	$ 339.4	$ 354.6	$ 702.0	$ 728.8
Gas	29.8	43.7	141.0	179.4
Other	13.0	13.6	28.2	32.6
Total operating revenues	382.2	411.9	871.2	940.8
Utility:
Electric production fuel and purchased power	90.5	122.9	200.6	262.9
Electric transmission service	77.9	75.4	161.8	159.0
Cost of gas sold	13.0	25.7	84.0	113.8
Other operation and maintenance	100.6	92.1	193.2	189.3
Depreciation and amortization	52.1	48.9	103.9	97.6
Taxes other than income taxes	14.3	12.9	28.4	26.7
Total operating expenses	348.4	377.9	771.9	849.3
Operating income	33.8	34.0	99.3	91.5
Interest expense and other:
Interest expense	23.9	22.6	48.0	45.1
Allowance for funds used during construction	(6.7)	(6.0)	(12.0)	(12.0)
Interest income and other	0.0	(0.1)	(0.1)	(0.1)
Total interest expense and other	17.2	16.5	35.9	33.0
Income from continuing operations before income taxes	16.6	17.5	63.4	58.5
Income tax expense (benefit)	(2.6)	(3.4)	(6.2)	(8.4)
Net income (loss)	19.2	20.9	69.6	66.9
Preferred dividend requirements of IPL	2.5	2.5	5.1	5.1
Net income (loss) attributable to common shareowners	16.7	18.4	64.5	61.8
Amounts attributable to common shareowners:
Net income (loss) attributable to common shareowners	16.7	18.4	64.5	61.8
WPL [Member]
Utility:
Electric	301.0	289.3	609.7	590.9
Gas	21.9	33.2	109.1	138.2
Other	1.8	2.0	3.0	5.8
Total operating revenues	324.7	324.5	721.8	734.9
Utility:
Electric production fuel and purchased power	94.7	91.2	200.5	189.9
Electric transmission service	39.0	30.1	78.3	60.6
Cost of gas sold	8.9	19.3	68.7	93.1
Other operation and maintenance	56.7	68.6	110.7	132.4
Depreciation and amortization	45.8	44.7	91.8	89.4
Taxes other than income taxes	11.3	10.6	22.7	21.8
Total operating expenses	256.4	264.5	572.7	587.2
Operating income	68.3	60.0	149.1	147.7
Interest expense and other:
Interest expense	23.3	21.1	46.4	42.2
Equity income from unconsolidated investments, net	(11.3)	(11.4)	(19.1)	(22.8)
Allowance for funds used during construction	(1.9)	(2.4)	(3.4)	(5.5)
Interest income and other	(0.1)	0.3	0.0	0.3
Total interest expense and other	10.0	7.6	23.9	14.2
Income from continuing operations before income taxes	58.3	52.4	125.2	133.5
Income tax expense (benefit)	18.8	17.8	40.9	44.1
Net income (loss)	39.5	34.6	84.3	89.4
Net income attributable to noncontrolling interest	0.5	0.0	0.7	0.0
Net income (loss) attributable to common shareowners	39.0	34.6	83.6	89.4
Amounts attributable to common shareowners:
Net income (loss) attributable to common shareowners	$ 39.0	$ 34.6	$ 83.6	$ 89.4