Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred tax liabilities, property	$ 2,453	$ 2,442
Deferred tax liabilities, other	213	155
Total deferred tax liabilities	2,793	2,722
Deferred tax assets, federal credit carryforwards	649	672
Deferred tax assets, net operating losses carryforwards - state	26	32
Deferred tax assets, other	79	75
Subtotal deferred tax assets	754	779
Deferred tax assets, valuation allowances	(3)	0
Total deferred tax assets	751	779
Total deferred tax liabilities, net	2,042	1,943
IPL [Member]
Deferred tax liabilities, property	1,415	1,440
Deferred tax liabilities, other	157	86
Total deferred tax liabilities	1,572	1,526
Deferred tax assets, federal credit carryforwards	449	450
Deferred tax assets, net operating losses carryforwards - state	1	0
Deferred tax assets, other	32	29
Subtotal deferred tax assets	482	479
Deferred tax assets, valuation allowances	(1)	0
Total deferred tax assets	481	479
Total deferred tax liabilities, net	1,091	1,047
WPL [Member]
Deferred tax liabilities, property	972	938
Deferred tax liabilities, other	64	80
Total deferred tax liabilities	1,036	1,018
Deferred tax assets, federal credit carryforwards	191	209
Deferred tax assets, net operating losses carryforwards - state	0	0
Deferred tax assets, other	19	20
Subtotal deferred tax assets	210	229
Deferred tax assets, valuation allowances	(1)	0
Total deferred tax assets	209	229
Total deferred tax liabilities, net	827	789
ATC Holdings [Member]
Deferred tax liabilities, ATC Holdings	127	125
ATC Holdings [Member] | IPL [Member]
Deferred tax liabilities, ATC Holdings	0	0
ATC Holdings [Member] | WPL [Member]
Deferred tax liabilities, ATC Holdings	$ 0	$ 0