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Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | $ 763.1 | $ 790.2 | $ 1,678.8 | $ 1,777.4
Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 675.2 | 691.2 | 1,405.5 | 1,434.6
Electric [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 249.7 | 233.3 | 516.5 | 508.0
Electric [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 164.0 | 171.3 | 346.3 | 352.4
Electric [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 197.3 | 214.2 | 407.2 | 422.9
Electric [Member] | Wholesale [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 39.1 | 41.0 | 80.0 | 87.5
Electric [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 25.1 | 31.4 | 55.5 | 63.8
Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 58.9 | 65.2 | 211.1 | 281.0
Gas [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 33.6 | 35.2 | 124.1 | 167.0
Gas [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 14.7 | 16.1 | 60.4 | 79.7
Gas [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 1.7 | 2.0 | 5.9 | 7.4
Gas [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.9 | 11.9 | 20.7 | 26.9
Other Utility [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 10.1 | 10.9 | 21.7 | 22.0
Other Utility [Member] | Steam [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.6 | 9.2 | 18.6 | 17.6
Other Utility [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 1.5 | 1.7 | 3.1 | 4.4
Non-utility and Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 18.9 | 22.9 | 40.5 | 39.8
Non-utility and Other [Member] | Transportation and other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 18.9 | 22.9 | 40.5 | 39.8
IPL [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 431.9 | 441.2 | 950.8 | 996.3
IPL [Member] | Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 388.4 | 392.3 | 813.2 | 812.1
IPL [Member] | Electric [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 135.3 | 125.9 | 282.7 | 273.4
IPL [Member] | Electric [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 109.0 | 111.4 | 228.7 | 228.0
IPL [Member] | Electric [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 114.3 | 118.4 | 235.5 | 234.5
IPL [Member] | Electric [Member] | Wholesale [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 13.0 | 14.6 | 27.4 | 31.5
IPL [Member] | Electric [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 16.8 | 22.0 | 38.9 | 44.7
IPL [Member] | Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 33.9 | 38.4 | 116.9 | 163.0
IPL [Member] | Gas [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 18.5 | 20.0 | 67.3 | 97.9
IPL [Member] | Gas [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.3 | 8.8 | 32.4 | 43.6
IPL [Member] | Gas [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 1.3 | 1.6 | 3.6 | 4.8
IPL [Member] | Gas [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 5.8 | 8.0 | 13.6 | 16.7
IPL [Member] | Other Utility [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 9.6 | 10.5 | 20.7 | 21.2
IPL [Member] | Other Utility [Member] | Steam [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.6 | 9.2 | 18.6 | 17.6
IPL [Member] | Other Utility [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 1.0 | 1.3 | 2.1 | 3.6
WPL [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 312.3 | 326.1 | 687.5 | 741.3
WPL [Member] | Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 286.8 | 298.9 | 592.3 | 622.5
WPL [Member] | Electric [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 114.4 | 107.4 | 233.8 | 234.6
WPL [Member] | Electric [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 55.0 | 59.9 | 117.6 | 124.4
WPL [Member] | Electric [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 83.0 | 95.8 | 171.7 | 188.4
WPL [Member] | Electric [Member] | Wholesale [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 26.1 | 26.4 | 52.6 | 56.0
WPL [Member] | Electric [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 8.3 | 9.4 | 16.6 | 19.1
WPL [Member] | Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 25.0 | 26.8 | 94.2 | 118.0
WPL [Member] | Gas [Member] | Retail - residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 15.1 | 15.2 | 56.8 | 69.1
WPL [Member] | Gas [Member] | Retail - commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 6.4 | 7.3 | 28.0 | 36.1
WPL [Member] | Gas [Member] | Retail - industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 0.4 | 0.4 | 2.3 | 2.6
WPL [Member] | Gas [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 3.1 | 3.9 | 7.1 | 10.2
WPL [Member] | Other Utility [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 0.5 | 0.4 | 1.0 | 0.8
WPL [Member] | Other Utility [Member] | Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | $ 0.5 | $ 0.4 | $ 1.0 | $ 0.8

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