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Variable Interest Entities (Narrative) (Details) |  |  | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
May 24, 2024 USD ($) | Mar. 18, 2024 USD ($) | Jun. 30, 2024 USD ($) Rate MW | Mar. 31, 2024 USD ($) | Jun. 30, 2023 USD ($) | Jun. 30, 2024 USD ($) Rate MW | Jun. 30, 2023 USD ($) | Dec. 31, 2023 USD ($)
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Wind Power Purchase Agreement, Purchase Percentage | Rate |  |  | 100.00% |  |  | 100.00% |  |
Payments to Acquire Assets, Investing Activities | $ 114.9 | $ 110,600,000 |  |  |  |  |  |
Business Acquisition, Transaction Costs |  |  |  |  |  |  |  | $ 54,700,000
Proceeds from Contributed Capital |  |  |  | $ 2,160,000,000 |  |  |  |
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount |  |  |  |  |  |  |  | 1,360,000,000
Income Taxes |  |  | $ 17,600,000 |  | $ 14,100,000 | $ 93,600,000 | $ 99,900,000 | $ 63,500,000
Contributions from NIPSCO minority interest holders |  |  | 59,700,000 |  |  |  |  |
Contributions from NIPSCO minority interest holders |  |  | $ 20,200,000 |  |  |  |  |
Rosewater |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Nameplate Capacity | MW |  |  | 102 |  |  | 102 |  |
Indiana Crossroads Wind |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Nameplate Capacity | MW |  |  | 302 |  |  | 302 |  |
Indiana Crossroads Solar |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Nameplate Capacity | MW |  |  | 200 |  |  | 200 |  |
Dunns Bridge I |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Nameplate Capacity | MW |  |  | 265 |  |  | 265 |  |

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