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Benefit Plans (Amounts Recognized On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
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Amounts recognized on the balance sheets consist of: |  |
Pension and other benefit obligations | $ (484.0) | $ (509.1)
Pension Plans, Defined Benefit [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Non-current assets | 0.0 | 0.0
Current liabilities | (14.3) | (2.3)
Pension and other benefit obligations | (335.0) | (364.1)
Net amounts recognized at December 31 | (349.3) | (366.4)
Amounts recognized in Regulatory Assets consist of: |  |
Net actuarial loss | 485.3 | 505.2
Prior service credit | (5.1) | (5.8)
Net amount recognized at December 31 | 480.2 | 499.4
Other Postretirement Benefits Plans [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Non-current assets | 9.8 | 7.5
Current liabilities | (8.1) | (9.6)
Pension and other benefit obligations | (110.4) | (104.9)
Net amounts recognized at December 31 | (108.7) | (107.0)
Amounts recognized in Regulatory Assets consist of: |  |
Net actuarial loss | 45.2 | 44.5
Prior service credit | (0.9) | (1.1)
Net amount recognized at December 31 | 44.3 | 43.4
IPL [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Pension and other benefit obligations | (167.7) | (178.4)
IPL [Member] | Pension Plans, Defined Benefit [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Non-current assets | 0.0 | 0.0
Current liabilities | (0.5) | (0.6)
Pension and other benefit obligations | (144.7) | (155.5)
Net amounts recognized at December 31 | (145.2) | (156.1)
Amounts recognized in Regulatory Assets consist of: |  |
Net actuarial loss | 208.2 | 218.8
Prior service credit | (1.7) | (1.8)
Net amount recognized at December 31 | 206.5 | 217.0
IPL [Member] | Other Postretirement Benefits Plans [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Non-current assets | 6.6 | 4.7
Current liabilities | (1.8) | (1.9)
Pension and other benefit obligations | (18.6) | (18.6)
Net amounts recognized at December 31 | (13.8) | (15.8)
Amounts recognized in Regulatory Assets consist of: |  |
Net actuarial loss | 16.6 | 18.8
Prior service credit | 0.0 | 0.0
Net amount recognized at December 31 | 16.6 | 18.8
WPL [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Pension and other benefit obligations | (210.8) | (217.7)
WPL [Member] | Pension Plans, Defined Benefit [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Non-current assets | 0.0 | 0.0
Current liabilities | (0.1) | (0.1)
Pension and other benefit obligations | (144.0) | (154.3)
Net amounts recognized at December 31 | (144.1) | (154.4)
Amounts recognized in Regulatory Assets consist of: |  |
Net actuarial loss | 212.0 | 223.0
Prior service credit | (1.2) | (1.3)
Net amount recognized at December 31 | 210.8 | 221.7
WPL [Member] | Other Postretirement Benefits Plans [Member] |  |
Amounts recognized on the balance sheets consist of: |  |
Non-current assets | 3.2 | 2.8
Current liabilities | (6.0) | (7.4)
Pension and other benefit obligations | (65.4) | (61.9)
Net amounts recognized at December 31 | (68.2) | (66.5)
Amounts recognized in Regulatory Assets consist of: |  |
Net actuarial loss | 22.2 | 19.9
Prior service credit | (0.9) | (1.1)
Net amount recognized at December 31 | $ 21.3 | $ 18.8

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