Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Utility:
Electric	$ 2,689.0	$ 2,589.3	$ 2,635.8
Gas	464.8	396.3	476.7
Other	71.3	56.7	62.0
Non-regulated	51.7	52.2	46.9
Total operating revenues	3,276.8	3,094.5	3,221.4
Utility:
Electric production fuel and energy purchases	725.0	712.3	764.5
Purchased electric capacity	216.8	271.5	257.2
Electric transmission service	418.3	341.3	323.8
Cost of gas sold	276.7	217.2	295.2
Other operation and maintenance	620.7	590.0	630.2
Non-regulated operation and maintenance	14.9	11.9	18.0
Depreciation and amortization	370.9	332.4	321.0
Taxes other than income taxes	99.6	98.2	98.2
Total operating expenses	2,742.9	2,574.8	2,708.1
Operating income	533.9	519.7	513.3
Interest expense and other:
Interest expense	172.8	156.7	158.3
Equity (income) loss from unconsolidated investments, net	(43.7)	(41.3)	(39.3)
Allowance for funds used during construction	(30.8)	(21.9)	(12.0)
Interest income and other	(0.4)	(4.0)	(4.3)
Total interest expense and other	97.9	89.5	102.7
Income from continuing operations before income taxes	436.0	430.2	410.6
Income tax expense (benefit)	53.9	89.4	69.2
Income from continuing operations, net of tax	382.1	340.8	341.4
Loss from discontinued operations, net of tax	(5.9)	(5.1)	(19.5)
Net income	376.2	335.7	321.9
Preferred dividend requirements of subsidiaries	17.9	15.9	18.3
Net income (loss) attributable to common shareowners	358.3	319.8	303.6
Weighted average number of common shares outstanding (basic and diluted) (000s) (in shares)	110.8	110.8	110.7
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)	$ 3.29	$ 2.93	$ 2.92
Loss from discontinued operations, net of tax (in dollars per share)	$ (0.06)	$ (0.04)	$ (0.18)
Net income (in dollars per share)	$ 3.23	$ 2.89	$ 2.74
Amounts attributable to common shareowners:
Income from continuing operations, net of tax	364.2	324.9	323.1
Loss from discontinued operations, net of tax	(5.9)	(5.1)	(19.5)
Net income (loss) attributable to common shareowners	358.3	319.8	303.6
IPL [Member]
Utility:
Electric	1,491.8	1,371.1	1,408.3
Gas	273.9	226.7	276.3
Other	53.1	52.5	55.5
Total operating revenues	1,818.8	1,650.3	1,740.1
Utility:
Electric production fuel and energy purchases	382.1	344.5	383.1
Purchased electric capacity	155.2	153.7	147.7
Electric transmission service	301.4	235.0	219.2
Cost of gas sold	160.3	124.9	175.6
Other operation and maintenance	362.3	350.0	375.0
Depreciation and amortization	191.1	188.9	179.1
Taxes other than income taxes	54.4	53.0	52.0
Total operating expenses	1,606.8	1,450.0	1,531.7
Operating income	212.0	200.3	208.4
Interest expense and other:
Interest expense	81.3	78.5	78.7
Allowance for funds used during construction	(21.0)	(8.4)	(5.8)
Interest income and other	(0.3)	(0.2)	(0.2)
Total interest expense and other	60.0	69.9	72.7
Income from continuing operations before income taxes	152.0	130.4	135.7
Income tax expense (benefit)	(37.9)	(19.8)	(3.6)
Net income	189.9	150.2	139.3
Preferred dividend requirements of subsidiaries	16.3	12.6	15.0
Net income (loss) attributable to common shareowners	173.6	137.6	124.3
Amounts attributable to common shareowners:
Net income (loss) attributable to common shareowners	173.6	137.6	124.3
WPL [Member]
Utility:
Electric	1,197.2	1,218.2	1,227.5
Gas	190.9	169.6	200.4
Other	18.2	4.2	6.5
Total operating revenues	1,406.3	1,392.0	1,434.4
Utility:
Electric production fuel and energy purchases	342.9	367.8	381.4
Purchased electric capacity	61.6	117.8	109.5
Electric transmission service	116.9	106.3	104.6
Cost of gas sold	116.4	92.3	119.6
Other operation and maintenance	258.4	240.0	255.2
Depreciation and amortization	172.2	140.9	140.1
Taxes other than income taxes	41.8	42.1	43.6
Total operating expenses	1,110.2	1,107.2	1,154.0
Operating income	296.1	284.8	280.4
Interest expense and other:
Interest expense	85.0	80.2	79.9
Equity (income) loss from unconsolidated investments, net	(43.7)	(42.1)	(38.7)
Allowance for funds used during construction	(9.8)	(13.5)	(6.2)
Interest income and other	(0.1)	(0.1)	0
Total interest expense and other	31.4	24.5	35.0
Income from continuing operations before income taxes	264.7	260.3	245.4
Income tax expense (benefit)	87.2	94.6	81.9
Net income	177.5	165.7	163.5
Preferred dividend requirements of subsidiaries	1.6	3.3	3.3
Net income (loss) attributable to common shareowners	175.9	162.4	160.2
Amounts attributable to common shareowners:
Net income (loss) attributable to common shareowners	$ 175.9	$ 162.4	$ 160.2