Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	2.00%	3.00%	2.00%
Production tax credits	(17.00%)	(18.00%)	(17.00%)
Amortization of excess deferred taxes	(2.00%)	(2.00%)	(18.00%)
Effect of rate-making on property-related differences	(4.00%)	(1.00%)	(1.00%)
Adjustment for prior period taxes	0.00%	1.00%	1.00%
Other items, net	1.00%	(1.00%)	0.00%
Overall income tax rate	1.00%	3.00%	(12.00%)
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	(2.00%)	(2.00%)	(1.00%)
Production tax credits	(31.00%)	(34.00%)	(27.00%)
Amortization of excess deferred taxes	(2.00%)	(2.00%)	(4.00%)
Effect of rate-making on property-related differences	(5.00%)	(1.00%)	(2.00%)
Adjustment for prior period taxes	0.00%	1.00%	2.00%
Other items, net	0.00%	1.00%	0.00%
Overall income tax rate	(19.00%)	(16.00%)	(11.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	5.00%	6.00%	6.00%
Production tax credits	(7.00%)	(5.00%)	(6.00%)
Amortization of excess deferred taxes	(2.00%)	(3.00%)	(43.00%)
Effect of rate-making on property-related differences	(3.00%)	(2.00%)	(1.00%)
Adjustment for prior period taxes	0.00%	0.00%	0.00%
Other items, net	1.00%	0.00%	(1.00%)
Overall income tax rate	15.00%	17.00%	(24.00%)