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Debt (Long-term Debt) (Details) - USD ($) $ in Millions | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | --- | ---
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 9,925 | $ 9,109
Current maturities |  | (1,171) | (809)
Unamortized debt issuance costs |  | (55) | (54)
Unamortized debt (discount) and premium, net |  | (22) | (21)
Long-term debt, net |  | 8,677 | 8,225
Senior Debentures [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | 4,125 | 3,975
Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 250 | $ 250
Interest rate, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 3.60% | 3.60%
Senior Debentures [Member] | 2.3% senior debenture, due 2030 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 400 | $ 400
Interest rate, percent |  | 2.30% | 2.30%
Senior Debentures [Member] | 5.7%, senior debentures, due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 5.70% | 5.70%
Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 100 | $ 100
Interest rate, percent |  | 6.45% | 6.45%
Senior Debentures [Member] | 4.95% senior debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 |
Interest rate, percent |  | 4.95% |
Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 125 | $ 125
Interest rate, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 3.50% | 3.50%
Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 3.10% | 3.10%
Senior Debentures [Member] | 5.45% senior debenture, due 2054 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 |
Interest rate, percent |  | 5.45% |
Senior Debentures [Member] | 3.25% senior debenture, retired in 2024 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  |  | $ 500
Interest rate, percent |  |  | 3.25%
Debentures [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 3,400 | $ 3,100
Debentures [Member] | 3.05% debenture, due 2027 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 3.05% | 3.05%
Debentures [Member] | 3% debenture, due 2029 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 | $ 350
Interest rate, percent |  | 3.00% | 3.00%
Debentures [Member] | 1.95% debenture, due 2031 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 1.95% | 1.95%
Debentures [Member] | 3.95% debenture, due 2032 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 600 | $ 600
Interest rate, percent |  | 3.95% | 3.95%
Debentures [Member] | 4.95% debenture, due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 4.95% | 4.95%
Debentures [Member] | 5.375% debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 |
Interest rate, percent |  | 5.375% |
Debentures [Member] | 6.25% debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 100 | $ 100
Interest rate, percent |  | 6.25% | 6.25%
Debentures [Member] | 6.375% debenture, due 2037 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 6.375% | 6.375%
Debentures [Member] | 7.6% debenture, due 2038 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 250 | $ 250
Interest rate, percent |  | 7.60% | 7.60%
Debentures [Member] | 4.1% debenture, due 2044 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 250 | $ 250
Interest rate, percent |  | 4.10% | 4.10%
Debentures [Member] | 3.65% debenture, due 2050 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 | $ 350
Interest rate, percent |  | 3.65% | 3.65%
Senior Notes [Member] | 3.875% senior notes, due 2026 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 575 | $ 575
Interest rate, percent |  | 3.875% | 3.875%
Other Long Term Debt [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 2,400 | $ 2,034
IPL [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | 4,125 | 3,975
Current maturities |  | (300) | (500)
Unamortized debt issuance costs |  | (25) | (21)
Unamortized debt (discount) and premium, net |  | (10) | (9)
Long-term debt, net |  | 3,790 | 3,445
IPL [Member] | Senior Debentures [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | 4,125 | 3,975
IPL [Member] | Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 250 | $ 250
Interest rate, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 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
Interest rate, percent |  | 2.30% | 2.30%
IPL [Member] | Senior Debentures [Member] | 5.7%, senior debentures, due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 5.70% | 5.70%
IPL [Member] | Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 100 | $ 100
Interest rate, percent |  | 6.45% | 6.45%
IPL [Member] | Senior Debentures [Member] | 4.95% senior debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 |
Interest rate, percent |  | 4.95% |
IPL [Member] | Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 125 | $ 125
Interest rate, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 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
Interest rate, percent |  | 3.10% | 3.10%
IPL [Member] | Senior Debentures [Member] | 5.45% senior debenture, due 2054 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 |
Interest rate, percent |  | 5.45% |
IPL [Member] | Senior Debentures [Member] | 3.25% senior debenture, retired in 2024 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  |  | $ 500
Interest rate, percent |  |  | 3.25%
WPL [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 3,400 | $ 3,100
Current maturities |  | 0 | 0
Unamortized debt issuance costs |  | (20) | (19)
Unamortized debt (discount) and premium, net |  | (10) | (11)
Long-term debt, net |  | 3,370 | 3,070
WPL [Member] | Debentures [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | 3,400 | 3,100
WPL [Member] | Debentures [Member] | 3.05% debenture, due 2027 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 3.05% | 3.05%
WPL [Member] | Debentures [Member] | 3% debenture, due 2029 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 | $ 350
Interest rate, percent |  | 3.00% | 3.00%
WPL [Member] | Debentures [Member] | 1.95% debenture, due 2031 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 1.95% | 1.95%
WPL [Member] | Debentures [Member] | 3.95% debenture, due 2032 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 600 | $ 600
Interest rate, percent |  | 3.95% | 3.95%
WPL [Member] | Debentures [Member] | 4.95% debenture, due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 4.95% | 4.95%
WPL [Member] | Debentures [Member] | 5.375% debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 |
Interest rate, percent |  | 5.375% |
WPL [Member] | Debentures [Member] | 6.25% debenture, due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 100 | $ 100
Interest rate, percent |  | 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, percent |  | 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, percent |  | 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, percent |  | 4.10% | 4.10%
WPL [Member] | Debentures [Member] | 3.65% debenture, due 2050 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 | $ 350
Interest rate, percent |  | 3.65% | 3.65%
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2025, Variable Rate [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 |
Interest rate, percent |  | 6.00% |
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2025, Variable Rate [Member] | Forecast [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt | $ 100 |  |
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement, retired in 2024, Variable Rate [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  |  | $ 300
Interest rate, percent |  |  | 6.00%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 1.4% senior notes, due 2026 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 200 | $ 200
Interest rate, percent |  | 1.40% | 1.40%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 5.4% senior notes, due 2027 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 375 |
Interest rate, percent |  | 5.40% |
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, percent |  | 4.25% | 4.25%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 5.95% senior notes, due 2029 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 300 | $ 300
Interest rate, percent |  | 5.95% | 5.95%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.6% senior notes, due 2032 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  | $ 350 | $ 350
Interest rate, percent |  | 3.60% | 3.60%
Sheboygan Power, LLC [Member] | Senior Secured Notes [Member] | 5.06% senior secured notes, retired in 2024 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt |  |  | $ 9
Interest rate, percent |  |  | 5.06%

X
- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -SubTopic 10 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-4 + Details
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- Definition Line items represent financial concepts included in a table. 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