Debt (Long-term Debt) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt	$ 9,109	$ 8,143
Current maturities	(809)	(408)
Unamortized debt issuance costs	(54)	(45)
Unamortized debt (discount) and premium, net	(21)	(22)
Long-term debt, net	8,225	7,668
Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,975	3,675
Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500
Interest rate, percent	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, 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	$ 0
Interest rate, percent	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] | 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%
Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,100	$ 2,800
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% debentures, due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 0
Interest rate, percent	4.95%
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%
Other Long Term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,034	$ 1,668
Senior Notes [Member] | 3.875% senior notes, due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 575	0
Interest rate, percent	3.875%
Other [Member] | Other, 1% at December 31, 2022, due 2024 to 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	1
Interest rate, percent	1.00%
IPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,975	3,675
Current maturities	(500)	0
Unamortized debt issuance costs	(21)	(21)
Unamortized debt (discount) and premium, net	(9)	(8)
Long-term debt, net	3,445	3,646
IPL [Member] | Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,975	3,675
IPL [Member] | Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500
Interest rate, percent	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, 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	$ 0
Interest rate, percent	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] | 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%
WPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,100	$ 2,800
Current maturities	0	0
Unamortized debt issuance costs	(19)	(19)
Unamortized debt (discount) and premium, net	(11)	(11)
Long-term debt, net	3,070	2,770
WPL [Member] | Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,100	2,800
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% debentures, due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 0
Interest rate, percent	4.95%
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 2024, Variable Rate [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 400
Interest rate, percent	6.00%
Payments to retire long-term debt	$ 100
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, percent	3.93%
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] | 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	$ 0
Interest rate, percent	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%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.75% senior notes, retired in 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	$ 400
Interest rate, percent		3.75%
Sheboygan Power, LLC [Member] | Senior Secured Notes [Member] | 5.06% senior secured notes, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 9	$ 17
Interest rate, percent	5.06%	5.06%