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Debt (Narrative) (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Jan. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, current borrowing capacity |  |  | $ 1,000 |
Long-term debt |  |  | 8,143 | $ 7,425
Parent Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, current borrowing capacity |  |  | 500 |
IPL [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, current borrowing capacity |  |  | 100 |
Long-term debt |  |  | 3,675 | 3,675
WPL [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, current borrowing capacity |  |  | 400 |
Long-term debt |  |  | $ 2,800 | $ 2,450
Alliant Energy Finance, LLC [Member] | Term loan credit agreement through January 2024 [Member] | Term Loan Credit Agreement [Member] | Subsequent Event |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt |  | $ 50 |  |
Forecast [Member] | Parent Company [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, maximum borrowing capacity | $ 500 |  |  |
Forecast [Member] | IPL [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, maximum borrowing capacity | 400 |  |  |
Forecast [Member] | WPL [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Line of credit facility, maximum borrowing capacity | $ 500 |  |  |

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- 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://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI https://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 + Details
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- Definition Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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