Condensed Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Utility:
Electric	$ 771.2	$ 798.1	$ 2,090.9	$ 2,043.4
Gas	47.2	39.8	364.8	310.5
Other	12.2	17.4	50.6	52.4
Non-regulated	12.5	11.3	39.9	37.9
Total operating revenues	843.1	866.6	2,546.2	2,444.2
Utility:
Electric production fuel and energy purchases	230.7	205.4	658.7	542.5
Purchased electric capacity	0.1	58.6	24.9	167.6
Electric transmission service	114.0	110.5	333.6	313.8
Cost of gas sold	21.8	14.3	228.7	181.2
Other operation and maintenance	156.7	156.3	478.4	453.7
Non-regulated operation and maintenance	2.3	3.1	5.4	8.4
Depreciation and amortization	97.1	92.1	288.4	277.4
Taxes other than income taxes	25.6	24.9	75.8	74.3
Total operating expenses	648.3	665.2	2,093.9	2,018.9
Operating income	194.8	201.4	452.3	425.3
Interest expense and other:
Interest expense	44.6	42.5	134.9	127.6
Equity income from unconsolidated investments, net	(11.5)	(11.1)	(34.2)	(32.7)
Allowance for funds used during construction	(8.3)	(8.5)	(25.8)	(21.1)
Interest income and other	(0.2)	(0.6)	(1.8)	(1.7)
Total interest expense and other	24.6	22.3	73.1	72.1
Income from continuing operations before income taxes	170.2	179.1	379.2	353.2
Income tax expense (benefit)	12.4	17.6	46.2	40.2
Income from continuing operations, net of tax	157.8	161.5	333.0	313.0
Income (loss) from discontinued operations, net of tax	(1.9)	(1.3)	(2.2)	(4.9)
Net income (loss)	155.9	160.2	330.8	308.1
Preferred dividend requirements of subsidiaries	2.6	2.6	7.7	15.3
Net income (loss) attributable to common shareowners	153.3	157.6	323.1	292.8
Weighted average number of common shares outstanding (basic and diluted) (in shares)	110.8	110.8	110.8	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)	$ 1.40	$ 1.43	$ 2.94	$ 2.69
Income (loss) from discontinued operations, net of tax (in dollars per share)	$ (0.02)	$ (0.01)	$ (0.02)	$ (0.05)
Net income (in dollars per share)	$ 1.38	$ 1.42	$ 2.92	$ 2.64
Amounts attributable to common shareowners:
Income from continuing operations, net of tax	155.2	158.9	325.3	297.7
Income (loss) from discontinued operations, net of tax	(1.9)	(1.3)	(2.2)	(4.9)
Net income (loss) attributable to common shareowners	153.3	157.6	323.1	292.8
Dividends declared per common share (in dollars per share)	$ 0.51	$ 0.47	$ 1.53	$ 1.41
IPL [Member]
Utility:
Electric	435.9	457.6	1,164.7	1,137.4
Gas	28.7	24.6	208.1	180.9
Other	11.6	12.2	44.2	37.4
Total operating revenues	476.2	494.4	1,417.0	1,355.7
Utility:
Electric production fuel and energy purchases	132.1	110.9	370.2	282.5
Purchased electric capacity	0.1	42.7	24.9	120.3
Electric transmission service	82.7	80.0	241.7	226.0
Cost of gas sold	14.6	9.3	128.4	103.2
Other operation and maintenance	89.8	90.5	279.1	264.2
Depreciation and amortization	49.3	47.6	146.9	142.8
Taxes other than income taxes	13.7	13.4	40.4	40.9
Total operating expenses	382.3	394.4	1,231.6	1,179.9
Operating income	93.9	100.0	185.4	175.8
Interest expense and other:
Interest expense	21.9	19.6	67.0	58.9
Allowance for funds used during construction	(6.6)	(5.8)	(18.6)	(14.3)
Interest income and other	0	0	(0.1)	(0.2)
Total interest expense and other	15.3	13.8	48.3	44.4
Income from continuing operations before income taxes	78.6	86.2	137.1	131.4
Income tax expense (benefit)	(26.5)	(26.4)	(34.9)	(37.4)
Net income (loss)	105.1	112.6	172.0	168.8
Preferred dividend requirements of subsidiaries	2.6	2.6	7.7	13.7
Net income (loss) attributable to common shareowners	102.5	110.0	164.3	155.1
Amounts attributable to common shareowners:
Net income (loss) attributable to common shareowners	102.5	110.0	164.3	155.1
WPL [Member]
Utility:
Electric	335.3	340.5	926.2	906.0
Gas	18.5	15.2	156.7	129.6
Other	0.6	5.2	6.4	15.0
Total operating revenues	354.4	360.9	1,089.3	1,050.6
Utility:
Electric production fuel and energy purchases	98.6	94.5	288.5	260.0
Purchased electric capacity	0	15.9	0	47.3
Electric transmission service	31.3	30.5	91.9	87.8
Cost of gas sold	7.2	5.0	100.3	78.0
Other operation and maintenance	66.9	65.8	199.3	189.5
Depreciation and amortization	45.6	42.7	135.0	129.0
Taxes other than income taxes	10.9	10.6	32.7	30.7
Total operating expenses	260.5	265.0	847.7	822.3
Operating income	93.9	95.9	241.6	228.3
Interest expense and other:
Interest expense	21.0	21.2	63.2	63.8
Equity income from unconsolidated investments, net	(11.4)	(11.1)	(34.2)	(32.7)
Allowance for funds used during construction	(1.7)	(2.7)	(7.2)	(6.8)
Interest income and other	0.5	0	0.8	0
Total interest expense and other	8.4	7.4	22.6	24.3
Income from continuing operations before income taxes	85.5	88.5	219.0	204.0
Income tax expense (benefit)	23.9	27.2	68.0	64.7
Net income (loss)	61.6	61.3	151.0	139.3
Preferred dividend requirements of subsidiaries	0	0	0	1.6
Net income (loss) attributable to common shareowners	61.6	61.3	151.0	137.7
Amounts attributable to common shareowners:
Net income (loss) attributable to common shareowners	$ 61.6	$ 61.3	$ 151.0	$ 137.7