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v3.25.0.1

Debt (Narrative) (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2024 USD ($) Integer $ / shares shares | Dec. 31, 2025 USD ($) | Dec. 31, 2023 USD ($)
Debt Instrument [Line Items] |  |  |
Line of credit facility, current borrowing capacity | $ 1,300,000,000 |  |
Long-term debt | 9,925,000,000 |  | $ 9,109,000,000
Current maturities of long-term debt | 1,171,000,000 |  | 809,000,000
Long-term debt, fair value | $ 9,577,000,000 |  | 8,677,000,000
Convertible Debt [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Trading days | Integer | 20 |  |
Trading days consecutive | Integer | 30 |  |
3.875% senior notes, due 2026 [Member] | Convertible Debt [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt | $ 575,000,000 |  |
Interest rate, percent | 3.875% |  |
Trading days | Integer | 5 |  |
Trading days consecutive | Integer | 10 |  |
Principal amount of Notes conversion rate applied to | $ 1,000 |  |
Initial conversion ratio | 15.5461 |  |
Initial conversion price | $ / shares | $ 64.32 |  |
Fundamental change repurchase conversion price, percent | 100.00% |  |
Current maturities of long-term debt | $ 571,000,000 |  |
Long-term debt, carrying value |  |  | 568,000,000
Unamortized debt issuance costs | 4,000,000 |  | 7,000,000
Long-term debt, fair value | $ 591,000,000 |  | 572,000,000
Shares included in diluted earnings per share (in shares) | shares | 0 |  |
3.875% senior notes, due 2026 [Member] | Convertible Debt [Member] | Maximum [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Conversion price, percent | 130.00% |  |
Threshold, product of last report sale price of common stock and conversion rate | 98.00% |  |
Parent Company [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of credit facility, current borrowing capacity | $ 600,000,000 |  |
Current maturities of long-term debt | 571,000,000 |  | 0
IPL [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of credit facility, current borrowing capacity | 300,000,000 |  |
Long-term debt | 4,125,000,000 |  | 3,975,000,000
Current maturities of long-term debt | 300,000,000 |  | 500,000,000
Long-term debt, fair value | 3,736,000,000 |  | 3,664,000,000
WPL [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of credit facility, current borrowing capacity | 400,000,000 |  |
Long-term debt | 3,400,000,000 |  | 3,100,000,000
Current maturities of long-term debt | 0 |  | 0
Long-term debt, fair value | $ 3,170,000,000 |  | $ 2,933,000,000
Forecast [Member] | Parent Company [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of credit facility, maximum borrowing capacity |  | $ 1,000,000,000 |
Forecast [Member] | IPL [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of credit facility, maximum borrowing capacity |  | 400,000,000 |
Forecast [Member] | WPL [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of credit facility, maximum borrowing capacity |  | $ 500,000,000 |

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