Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 7,425	$ 6,833
Current maturities	(633)	(8)
Unamortized debt issuance costs	(42)	(41)
Unamortized debt (discount) and premium, net	(15)	(15)
Long-term debt, net	6,735	6,769
Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,675	3,375
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 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400
Interest rate	2.30%	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] \| 3.1% senior debenture, due 2051 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	3.10%
Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,450	$ 2,150
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] \| 1.95% debenture, due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	1.95%
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 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350
Interest rate	3.65%	3.65%
Other Long Term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,300	$ 1,308
Other [Member] \| Other, 1% at December 31, 2021, due 2022 to 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1	2
Interest rate	1.00%
IPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,675	3,375
Current maturities	0	0
Unamortized debt issuance costs	(23)	(22)
Unamortized debt (discount) and premium, net	(9)	(8)
Long-term debt, net	3,643	3,345
IPL [Member] \| Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,675	3,375
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 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400
Interest rate	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
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] \| 3.1% senior debenture, due 2051 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	3.10%
WPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,450	$ 2,150
Current maturities	(250)	0
Unamortized debt issuance costs	(15)	(14)
Unamortized debt (discount) and premium, net	(6)	(6)
Long-term debt, net	2,179	2,130
WPL [Member] \| Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	2,450	2,150
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] \| 1.95% debenture, due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	1.95%
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 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350
Interest rate	3.65%	3.65%
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	$ 300
Interest rate	1.00%
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 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 200	$ 200
Interest rate	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
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 2022 to 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 24	$ 31
Interest rate	5.06%	5.06%

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.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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