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Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2016 | Mar. 31, 2015
Segment Reporting Information [Line Items] |  |
Operating revenues | $ 843.8 | $ 897.4
Operating income (loss) | 145.9 | 152.9
Income (loss) from continuing operations, net of tax | 97.6 | 96.6
Loss from discontinued operations, net of tax | (1.1) | 0.0
Net income (loss) attributable to common shareowners | 96.5 | 96.6
IPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 458.7 | 489.0
Operating income (loss) | 62.0 | 65.5
Net income (loss) attributable to common shareowners | 45.6 | 47.5
WPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 375.6 | 397.1
Operating income (loss) | 78.8 | 80.8
Net income (loss) attributable to common shareowners | 46.5 | 44.9
Electric [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 668.9 | 671.3
Operating income (loss) | 109.8 | 104.7
Electric [Member] | IPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 361.6 | 362.6
Operating income (loss) | 43.4 | 40.3
Electric [Member] | WPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 307.3 | 308.7
Operating income (loss) | 66.4 | 64.4
Gas [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 152.2 | 198.4
Operating income (loss) | 28.8 | 36.3
Gas [Member] | IPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 84.2 | 111.2
Operating income (loss) | 15.8 | 20.6
Gas [Member] | WPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 68.0 | 87.2
Operating income (loss) | 13.0 | 15.7
Other Utilities [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 13.2 | 16.4
Operating income (loss) | 2.2 | 5.3
Other Utilities [Member] | IPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 12.9 | 15.2
Operating income (loss) | 2.8 | 4.6
Other Utilities [Member] | WPL [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 0.3 | 1.2
Operating income (loss) | (0.6) | 0.7
Utilities Business [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 834.3 | 886.1
Operating income (loss) | 140.8 | 146.3
Income (loss) from continuing operations, net of tax | 92.1 |
Loss from discontinued operations, net of tax | 0.0 |
Net income (loss) attributable to common shareowners | 92.1 | 92.4
Non-Regulated [Member] | Other Segments [Member] |  |
Segment Reporting Information [Line Items] |  |
Operating revenues | 9.5 | 11.3
Operating income (loss) | 5.1 | 6.6
Income (loss) from continuing operations, net of tax | 5.5 |
Loss from discontinued operations, net of tax | (1.1) |
Net income (loss) attributable to common shareowners | $ 4.4 | $ 4.2

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