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Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | $ 765.3 | $ 754.6 | $ 1,619.2 | $ 1,598.4
Operating income (loss) |  | 149.3 | 128.6 | 292.2 | 274.5
Income from continuing operations, net of tax |  | 94.3 | 84.4 | 193.3 | 182.0
Income (loss) from discontinued operations, net of tax |  | 0.0 | (0.5) | 1.4 | (1.6)
Net income attributable to common shareowners |  | 94.3 | 83.9 | 194.7 | 180.4
IPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 420.2 | 411.0 | 870.7 | 869.7
Operating income (loss) |  | 66.3 | 48.0 | 115.9 | 110.0
Net income attributable to common shareowners |  | 42.8 | 31.9 | 80.0 | 77.5
WPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 334.8 | 334.3 | 727.9 | 709.9
Operating income (loss) |  | 73.7 | 75.0 | 159.7 | 153.8
Net income attributable to common shareowners |  | 38.1 | 43.2 | 83.6 | 89.7
Electric [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues | [1] | 680.9 | 675.9 | 1,358.5 | 1,344.8
Operating income (loss) | [1] | 135.6 | 119.3 | 242.8 | 229.1
Electric [Member] | IPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 372.4 | 364.4 | 728.6 | 726.0
Operating income (loss) |  | 62.4 | 44.5 | 96.2 | 87.9
Electric [Member] | WPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 308.5 | 311.5 | 629.9 | 618.8
Operating income (loss) |  | 73.2 | 74.8 | 146.6 | 141.2
Gas [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues | [1] | 62.6 | 57.0 | 216.9 | 209.2
Operating income (loss) | [1] | 3.9 | 1.9 | 31.9 | 30.7
Gas [Member] | IPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 36.7 | 34.5 | 119.8 | 118.7
Operating income (loss) |  | 2.4 | 0.9 | 16.8 | 16.7
Gas [Member] | WPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 25.9 | 22.5 | 97.1 | 90.5
Operating income (loss) |  | 1.5 | 1.0 | 15.1 | 14.0
Other Utility [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues | [1] | 11.5 | 12.4 | 23.2 | 25.6
Operating income (loss) | [1] | 0.5 | 1.8 | 0.9 | 4.0
Other Utility [Member] | IPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 11.1 | 12.1 | 22.3 | 25.0
Operating income (loss) |  | 1.5 | 2.6 | 2.9 | 5.4
Other Utility [Member] | WPL [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 0.4 | 0.3 | 0.9 | 0.6
Operating income (loss) |  | (1.0) | (0.8) | (2.0) | (1.4)
Utility Business [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues | [1] | 755.0 | 745.3 | 1,598.6 | 1,579.6
Operating income (loss) | [1] | 140.0 | 123.0 | 275.6 | 263.8
Income from continuing operations, net of tax | [1] |  | 75.1 | 177.2 | 167.2
Income (loss) from discontinued operations, net of tax | [1] |  | 0.0 | 0.0 | 0.0
Net income attributable to common shareowners | [1] | 87.6 | 75.1 | 177.2 | 167.2
Non-Regulated [Member] | Other Segments [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Operating revenues |  | 10.3 | 9.3 | 20.6 | 18.8
Operating income (loss) |  | 9.3 | 5.6 | 16.6 | 10.7
Income from continuing operations, net of tax |  |  | 9.3 | 16.1 | 14.8
Income (loss) from discontinued operations, net of tax |  |  | (0.5) | 1.4 | (1.6)
Net income attributable to common shareowners |  | $ 6.7 | $ 8.8 | $ 17.5 | $ 13.2
[1] | Alliant Energy’s utility business segments include: a) utility electric operations, which include Alliant Energy’s entire investment in ATC; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business.

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