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v3.23.1

Debt (Narrative) (Details) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2023 USD ($) Integer $ / shares shares | Dec. 31, 2022 USD ($)
Debt [Line Items] |  |
Line of credit facility, current borrowing capacity | $ 1,000,000,000 |
Long-term debt, fair value | 8,462,000,000 | $ 7,339,000,000
Parent Company [Member] |  |
Debt [Line Items] |  |
Line of credit facility, current borrowing capacity | 450,000,000 |
IPL [Member] |  |
Debt [Line Items] |  |
Line of credit facility, current borrowing capacity | 250,000,000 |
Long-term debt, fair value | 3,335,000,000 | 3,228,000,000
WPL [Member] |  |
Debt [Line Items] |  |
Line of credit facility, current borrowing capacity | 300,000,000 |
Long-term debt, fair value | 2,939,000,000 | $ 2,542,000,000
Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024 [Member] | Alliant Energy Finance LLC [Member] |  |
Debt [Line Items] |  |
Long-term debt | 50,000,000 |
Debentures [Member] | 4.95% debenture, due 2033 [Member] | WPL [Member] |  |
Debt [Line Items] |  |
Long-term debt | $ 300,000,000 |
Interest rate, percent | 4.95% |
Convertible Senior Notes [Member] |  |
Debt [Line Items] |  |
Trading days | Integer | 20 |
Trading days consecutive | Integer | 30 |
Convertible Senior Notes [Member] | 3.875% convertible senior notes, due 2026 [Member] |  |
Debt [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% |
Long-term debt, carrying value | $ 565,000,000 |
Unamortized debt issuance costs | 10,000,000 |
Long-term debt, fair value | $ 595,000,000 |
Shares included in diluted earnings per share (in shares) | shares | 0 |
Convertible Senior Notes [Member] | 3.875% convertible senior notes, due 2026 [Member] | Maximum [Member] |  |
Debt [Line Items] |  |
Conversion price, percent | 130.00% |
Convertible Senior Notes [Member] | 3.875% convertible senior notes, due 2026 [Member] | Minimum [Member] |  |
Debt [Line Items] |  |
Conversion price, percent | 98.00% |

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