Segments Of Business (Schedule Of Segments Of Business) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Operating revenues	$ 843.1	$ 866.6	$ 2,546.2	$ 2,444.2
Operating income (loss)	194.8	201.4	452.3	425.3
Income (loss) 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
IPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	476.2	494.4	1,417.0	1,355.7
Operating income (loss)	93.9	100.0	185.4	175.8
Net income (loss) attributable to common shareowners	102.5	110.0	164.3	155.1
WPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	354.4	360.9	1,089.3	1,050.6
Operating income (loss)	93.9	95.9	241.6	228.3
Net income (loss) attributable to common shareowners	61.6	61.3	151.0	137.7
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	771.2	798.1	2,090.9	2,043.4
Operating income (loss)	190.8	199.6	374.2	359.1
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	435.9	457.6	1,164.7	1,137.4
Operating income (loss)	94.7	99.6	150.2	146.2
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	335.3	340.5	926.2	906.0
Operating income (loss)	96.1	100.0	224.0	212.9
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	47.2	39.8	364.8	310.5
Operating income (loss)	(4.4)	(3.4)	41.3	39.5
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	28.7	24.6	208.1	180.9
Operating income (loss)	(2.8)	(0.7)	22.1	22.6
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	18.5	15.2	156.7	129.6
Operating income (loss)	(1.6)	(2.7)	19.2	16.9
Other Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	12.2	17.4	50.6	52.4
Operating income (loss)	1.4	(0.3)	11.5	5.5
Other Utilities [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	11.6	12.2	44.2	37.4
Operating income (loss)	2.0	1.1	13.1	7.0
Other Utilities [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Operating revenues	0.6	5.2	6.4	15.0
Operating income (loss)	(0.6)	(1.4)	(1.6)	(1.5)
Utilities Business [Member]
Segment Reporting Information [Line Items]
Operating revenues	830.6	855.3	2,506.3	2,406.3
Operating income (loss)	187.8	195.9	427.0	404.1
Income (loss) from continuing operations, net of tax	164.1	171.3	315.3	292.8
Income (loss) from discontinued operations, net of tax	0	0	0	0
Net income (loss) attributable to common shareowners	164.1	171.3	315.3	292.8
Non-Regulated [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	12.5	11.3	39.9	37.9
Operating income (loss)	7.0	5.5	25.3	21.2
Income (loss) from continuing operations, net of tax	(8.9)	(12.4)	10.0	4.9
Income (loss) from discontinued operations, net of tax	(1.9)	(1.3)	(2.2)	(4.9)
Net income (loss) attributable to common shareowners	$ (10.8)	$ (13.7)	$ 7.8	$ 0