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v3.20.4

Debt (Long-term Debt) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Instrument [Line Items] |  |
Long-term debt | $ 6,833 | $ 6,240
Current maturities | (8) | (657)
Unamortized debt issuance costs | (41) | (37)
Unamortized debt (discount) and premium, net | (15) | (13)
Long-term debt, net | 6,769 | 5,533
Senior Debentures [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 3,375 | 3,175
Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 500 | $ 500
Interest rate | 3.25% | 3.25%
Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 3.40% | 3.40%
Senior Debentures [Member] | 5.5% senior debenture, due 2025 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 50 | $ 50
Interest rate | 5.50% | 5.50%
Senior Debentures [Member] | 4.1% senior debenture, due 2028 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 500 | $ 500
Interest rate | 4.10% | 4.10%
Senior Debentures [Member] | 3.6% senior debenture, due 2029 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 3.60% | 3.60%
Senior Debentures [Member] | 2.3% senior debenture, due 2030 |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 400 | $ 0
Interest rate | 2.30% |
Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 100 | $ 100
Interest rate | 6.45% | 6.45%
Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 125 | $ 125
Interest rate | 6.30% | 6.30%
Senior Debentures [Member] | 6.25% senior debenture, due 2039 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 6.25% | 6.25%
Senior Debentures [Member] | 4.7% senior debenture, due 2043 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 4.70% | 4.70%
Senior Debentures [Member] | 3.7% senior debenture, due 2046 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 3.70% | 3.70%
Senior Debentures [Member] | 3.5% senior debenture, due 2049 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 3.50% | 3.50%
Senior Debentures [Member] | 3.65% senior debenture, retired in 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 0 | $ 200
Interest rate |  | 3.65%
Debentures [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 2,150 | $ 1,950
Debentures [Member] | 2.25% debenture, due 2022 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 2.25% | 2.25%
Debentures [Member] | 3.05% debenture, due 2027 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 3.05% | 3.05%
Debentures [Member] | 3% debenture, due 2029 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 350 | $ 350
Interest rate | 3.00% | 3.00%
Debentures [Member] | 6.25% debenture, due 2034 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 100 | $ 100
Interest rate | 6.25% | 6.25%
Debentures [Member] | 6.375% debenture, due 2037 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 6.375% | 6.375%
Debentures [Member] | 7.6% debenture, due 2038 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 7.60% | 7.60%
Debentures [Member] | 4.1% debenture, due 2044 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 4.10% | 4.10%
Debentures [Member] | 3.65% debenture, due 2050 |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 350 | $ 0
Interest rate | 3.65% |
Debentures [Member] | 4.6% debenture, retired in 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 0 | $ 150
Interest rate |  | 4.60%
Other Long Term Debt [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 1,308 | $ 1,115
Other [Member] | Other, 1% at December 31, 2020, due 2021 to 2025 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 2 | 2
Interest rate | 1.00% |
IPL [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 3,375 | 3,175
Current maturities | 0 | (200)
Unamortized debt issuance costs | (22) | (21)
Unamortized debt (discount) and premium, net | (8) | (7)
Long-term debt, net | 3,345 | 2,947
IPL [Member] | Senior Debentures [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 3,375 | 3,175
IPL [Member] | Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 500 | $ 500
Interest rate | 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
Interest rate | 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
Interest rate | 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
Interest rate | 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
Interest rate | 3.60% | 3.60%
IPL [Member] | Senior Debentures [Member] | 2.3% senior debenture, due 2030 |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 400 | $ 0
Interest rate | 2.30% |
IPL [Member] | Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 100 | $ 100
Interest rate | 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
Interest rate | 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
Interest rate | 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
Interest rate | 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
Interest rate | 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
Interest rate | 3.50% | 3.50%
IPL [Member] | Senior Debentures [Member] | 3.65% senior debenture, retired in 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 0 | $ 200
Interest rate |  | 3.65%
WPL [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 2,150 | $ 1,950
Current maturities | 0 | (150)
Unamortized debt issuance costs | (14) | (11)
Unamortized debt (discount) and premium, net | (6) | (6)
Long-term debt, net | 2,130 | 1,783
WPL [Member] | Debentures [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 2,150 | 1,950
WPL [Member] | Debentures [Member] | 2.25% debenture, due 2022 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 2.25% | 2.25%
WPL [Member] | Debentures [Member] | 3.05% debenture, due 2027 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 3.05% | 3.05%
WPL [Member] | Debentures [Member] | 3% debenture, due 2029 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 350 | $ 350
Interest rate | 3.00% | 3.00%
WPL [Member] | Debentures [Member] | 6.25% debenture, due 2034 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 100 | $ 100
Interest rate | 6.25% | 6.25%
WPL [Member] | Debentures [Member] | 6.375% debenture, due 2037 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 300
Interest rate | 6.375% | 6.375%
WPL [Member] | Debentures [Member] | 7.6% debenture, due 2038 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 7.60% | 7.60%
WPL [Member] | Debentures [Member] | 4.1% debenture, due 2044 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 250 | $ 250
Interest rate | 4.10% | 4.10%
WPL [Member] | Debentures [Member] | 3.65% debenture, due 2050 |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 350 | $ 0
Interest rate | 3.65% |
WPL [Member] | Debentures [Member] | 4.6% debenture, retired in 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 0 | $ 150
Interest rate |  | 4.60%
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2022 |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 300 | $ 0
Interest rate | 1.00% |
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement, retired in 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 0 | $ 300
Interest rate |  | 2.00%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.75% senior notes, due 2023 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 400 | $ 400
Interest rate | 3.75% | 3.75%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 1.4% senior notes, due 2026 |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 200 | $ 0
Interest rate | 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
Interest rate | 4.25% | 4.25%
Corporate Services [Member] | Senior Notes [Member] | 3.45% senior notes, due 2022 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 75 | $ 75
Interest rate | 3.45% | 3.45%
Sheboygan Power, LLC [Member] | Senior Secured Notes [Member] | 5.06% senior secured notes, due 2021 to 2024 [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 31 | $ 38
Interest rate | 5.06% | 5.06%

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