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v3.21.1

Debt (Credit Facilities) (Details) $ in Millions | Mar. 31, 2021 USD ($)
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Debt [Line Items] |
Amount outstanding | $ 336
Weighted average interest rates | 0.20%
Available credit facility capacity | $ 664
IPL [Member] |
Debt [Line Items] |
Amount outstanding | 0
Available credit facility capacity | 250
WPL [Member] |
Debt [Line Items] |
Amount outstanding | $ 148
Weighted average interest rates | 0.10%
Available credit facility capacity | $ 152

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