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Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
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%	7.00%	7.00%
Production tax credits	(17.00%)	(9.00%)	(5.00%)
Amortization of excess deferred taxes	(13.00%)	(1.00%)	(1.00%)
Effect of rate-making on property-related differences	(3.00%)	(6.00%)	(8.00%)
Adjustment for prior period taxes	1.00%	1.00%	(2.00%)
Federal Tax Reform adjustments	0.00%	0.00%	(1.00%)
Other items, net	(1.00%)	(1.00%)	(1.00%)
Overall income tax rate	(10.00%)	11.00%	8.00%
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	(1.00%)	8.00%	8.00%
Production tax credits	(28.00%)	(13.00%)	(5.00%)
Amortization of excess deferred taxes	(5.00%)	0.00%	0.00%
Effect of rate-making on property-related differences	(4.00%)	(10.00%)	(14.00%)
Adjustment for prior period taxes	1.00%	3.00%	(5.00%)
Federal Tax Reform adjustments	0.00%	0.00%	0.00%
Other items, net	0.00%	0.00%	(1.00%)
Overall income tax rate	(16.00%)	8.00%	(1.00%)
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	6.00%	6.00%	6.00%
Production tax credits	(7.00%)	(5.00%)	(7.00%)
Amortization of excess deferred taxes	(26.00%)	(2.00%)	0.00%
Effect of rate-making on property-related differences	(2.00%)	(3.00%)	(2.00%)
Adjustment for prior period taxes	0.00%	0.00%	0.00%
Federal Tax Reform adjustments	0.00%	0.00%	(2.00%)
Other items, net	0.00%	0.00%	(1.00%)
Overall income tax rate	(8.00%)	17.00%	15.00%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	0.00%	(1.00%)	(2.00%)
IPL's tax benefit riders [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	0.00%	(1.00%)	(5.00%)

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