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Debt (Long-term Debt) (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Mar. 31, 2022
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 8,143 | $ 8,143 | $ 7,425 |  |
Current maturities | (408) | (408) | (633) |  |
Unamortized debt issuance costs | (45) | (45) | (42) |  |
Unamortized debt (discount) and premium, net | (22) | (22) | (15) |  |
Long-term debt, net | 7,668 | 7,668 | 6,735 |  |
Proceeds from issuance of long-term debt |  | 1,338 | 600 | $ 1,250 |
Senior Debentures [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 3,675 | 3,675 | 3,675 |  |
Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 500 | $ 500 | $ 500 |  |
Interest rate | 3.25% | 3.25% | 3.25% |  |
Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 3.40% | 3.40% | 3.40% |  |
Senior Debentures [Member] | 5.5% senior debenture, due 2025 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 50 | $ 50 | $ 50 |  |
Interest rate | 5.50% | 5.50% | 5.50% |  |
Senior Debentures [Member] | 4.1% senior debenture, due 2028 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 500 | $ 500 | $ 500 |  |
Interest rate | 4.10% | 4.10% | 4.10% |  |
Senior Debentures [Member] | 3.6% senior debenture, due 2029 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.60% | 3.60% | 3.60% |  |
Senior Debentures [Member] | 2.3% senior debenture, due 2030 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 400 | $ 400 | $ 400 |  |
Interest rate | 2.30% | 2.30% | 2.30% |  |
Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 100 | $ 100 | $ 100 |  |
Interest rate | 6.45% | 6.45% | 6.45% |  |
Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 125 | $ 125 | $ 125 |  |
Interest rate | 6.30% | 6.30% | 6.30% |  |
Senior Debentures [Member] | 6.25% senior debenture, due 2039 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 6.25% | 6.25% | 6.25% |  |
Senior Debentures [Member] | 4.7% senior debenture, due 2043 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 4.70% | 4.70% | 4.70% |  |
Senior Debentures [Member] | 3.7% senior debenture, due 2046 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.70% | 3.70% | 3.70% |  |
Senior Debentures [Member] | 3.5% senior debenture, due 2049 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.50% | 3.50% | 3.50% |  |
Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.10% | 3.10% | 3.10% |  |
Debentures [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 2,800 | $ 2,800 | $ 2,450 |  |
Debentures [Member] | 3.05% debenture, due 2027 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.05% | 3.05% | 3.05% |  |
Debentures [Member] | 3% debenture, due 2029 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 350 | $ 350 | $ 350 |  |
Interest rate | 3.00% | 3.00% | 3.00% |  |
Debentures [Member] | 1.95% debenture, due 2031 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 1.95% | 1.95% | 1.95% |  |
Debentures [Member] | 3.95% debenture, due 2032 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 600 | $ 600 | $ 0 |  |
Interest rate | 3.95% | 3.95% |  |  |
Debentures [Member] | 6.25% debenture, due 2034 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 100 | $ 100 | $ 100 |  |
Interest rate | 6.25% | 6.25% | 6.25% |  |
Debentures [Member] | 6.375% debenture, due 2037 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 6.375% | 6.375% | 6.375% |  |
Debentures [Member] | 7.6% debenture, due 2038 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 7.60% | 7.60% | 7.60% |  |
Debentures [Member] | 4.1% debenture, due 2044 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 4.10% | 4.10% | 4.10% |  |
Debentures [Member] | 3.65% debenture, due 2050 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 350 | $ 350 | $ 350 |  |
Interest rate | 3.65% | 3.65% | 3.65% |  |
Debentures [Member] | 2.25% debenture, due 2022 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 0 | $ 0 | $ 250 |  |
Interest rate |  |  | 2.25% |  |
Other Long Term Debt [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 1,668 | 1,668 | $ 1,300 |  |
Other [Member] | Other, 1% at December 31, 2022, due 2023 to 2025 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 1 | $ 1 | 1 |  |
Interest rate | 1.00% | 1.00% |  |  |
IPL [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 3,675 | $ 3,675 | 3,675 |  |
Current maturities | 0 | 0 | 0 |  |
Unamortized debt issuance costs | (21) | (21) | (23) |  |
Unamortized debt (discount) and premium, net | (8) | (8) | (9) |  |
Long-term debt, net | 3,646 | 3,646 | 3,643 |  |
Proceeds from issuance of long-term debt |  | 0 | 300 | 400 |
IPL [Member] | Senior Debentures [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 3,675 | 3,675 | 3,675 |  |
IPL [Member] | Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 500 | $ 500 | $ 500 |  |
Interest rate | 3.25% | 3.25% | 3.25% |  |
IPL [Member] | Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 3.40% | 3.40% | 3.40% |  |
IPL [Member] | Senior Debentures [Member] | 5.5% senior debenture, due 2025 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 50 | $ 50 | $ 50 |  |
Interest rate | 5.50% | 5.50% | 5.50% |  |
IPL [Member] | Senior Debentures [Member] | 4.1% senior debenture, due 2028 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 500 | $ 500 | $ 500 |  |
Interest rate | 4.10% | 4.10% | 4.10% |  |
IPL [Member] | Senior Debentures [Member] | 3.6% senior debenture, due 2029 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.60% | 3.60% | 3.60% |  |
IPL [Member] | Senior Debentures [Member] | 2.3% senior debenture, due 2030 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 400 | $ 400 | $ 400 |  |
Interest rate | 2.30% | 2.30% | 2.30% |  |
IPL [Member] | Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 100 | $ 100 | $ 100 |  |
Interest rate | 6.45% | 6.45% | 6.45% |  |
IPL [Member] | Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 125 | $ 125 | $ 125 |  |
Interest rate | 6.30% | 6.30% | 6.30% |  |
IPL [Member] | Senior Debentures [Member] | 6.25% senior debenture, due 2039 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 6.25% | 6.25% | 6.25% |  |
IPL [Member] | Senior Debentures [Member] | 4.7% senior debenture, due 2043 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 4.70% | 4.70% | 4.70% |  |
IPL [Member] | Senior Debentures [Member] | 3.7% senior debenture, due 2046 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.70% | 3.70% | 3.70% |  |
IPL [Member] | Senior Debentures [Member] | 3.5% senior debenture, due 2049 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.50% | 3.50% | 3.50% |  |
IPL [Member] | Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.10% | 3.10% | 3.10% |  |
WPL [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 2,800 | $ 2,800 | $ 2,450 |  |
Current maturities | 0 | 0 | (250) |  |
Unamortized debt issuance costs | (19) | (19) | (15) |  |
Unamortized debt (discount) and premium, net | (11) | (11) | (6) |  |
Long-term debt, net | 2,770 | 2,770 | 2,179 |  |
Proceeds from issuance of long-term debt |  | 588 | 300 | $ 350 |
WPL [Member] | Debentures [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 2,800 | 2,800 | 2,450 |  |
WPL [Member] | Debentures [Member] | 3.05% debenture, due 2027 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 3.05% | 3.05% | 3.05% |  |
WPL [Member] | Debentures [Member] | 3% debenture, due 2029 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 350 | $ 350 | $ 350 |  |
Interest rate | 3.00% | 3.00% | 3.00% |  |
WPL [Member] | Debentures [Member] | 1.95% debenture, due 2031 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 1.95% | 1.95% | 1.95% |  |
WPL [Member] | Debentures [Member] | 3.95% debenture, due 2032 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 600 | $ 600 | $ 0 |  |
Interest rate | 3.95% | 3.95% |  |  |
WPL [Member] | Debentures [Member] | 6.25% debenture, due 2034 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 100 | $ 100 | $ 100 |  |
Interest rate | 6.25% | 6.25% | 6.25% |  |
WPL [Member] | Debentures [Member] | 6.375% debenture, due 2037 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 6.375% | 6.375% | 6.375% |  |
WPL [Member] | Debentures [Member] | 7.6% debenture, due 2038 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 7.60% | 7.60% | 7.60% |  |
WPL [Member] | Debentures [Member] | 4.1% debenture, due 2044 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 250 | $ 250 | $ 250 |  |
Interest rate | 4.10% | 4.10% | 4.10% |  |
WPL [Member] | Debentures [Member] | 3.65% debenture, due 2050 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 350 | $ 350 | $ 350 |  |
Interest rate | 3.65% | 3.65% | 3.65% |  |
WPL [Member] | Debentures [Member] | 2.25% debenture, due 2022 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 0 | $ 0 | $ 250 |  |
Interest rate |  |  | 2.25% |  |
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.75% senior notes, due 2023 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 400 | $ 400 | $ 400 |  |
Interest rate | 3.75% | 3.75% | 3.75% |  |
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 1.4% senior notes, due 2026 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 200 | $ 200 | $ 200 |  |
Interest rate | 1.40% | 1.40% | 1.40% |  |
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 4.25% senior notes, due 2028 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 300 | $ 300 | $ 300 |  |
Interest rate | 4.25% | 4.25% | 4.25% |  |
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.6% senior notes, due 2032 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 350 | $ 350 | $ 0 |  |
Interest rate | 3.60% | 3.60% |  |  |
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024, Variable Rate [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 400 | $ 400 | 0 |  | $ 300
Interest rate | 5.00% | 5.00% |  |  |
Proceeds from issuance of long-term debt | $ 100 |  |  |  |
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2022 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 0 | $ 0 | $ 300 |  |
Interest rate |  |  | 1.00% |  |
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024, Fixed Rate [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate | 3.93% | 3.93% |  |  |
Sheboygan Power, LLC [Member] | Senior Secured Notes [Member] | 5.06% senior secured notes, due 2023 to 2024 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 17 | $ 17 | $ 24 |  |
Interest rate | 5.06% | 5.06% | 5.06% |  |
Corporate Services [Member] | Senior Notes [Member] | 3.45% senior notes, due 2022 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 0 | $ 0 | $ 75 |  |
Interest rate |  |  | 3.45% |  |

X
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