Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Income Tax [Line Items]
Deferred tax liabilities, property	$ 2,828	$ 2,596
Deferred tax liabilities, other	167	178
Total deferred tax liabilities	3,134	2,909
Deferred tax assets, federal credit carryforwards	669	605
Deferred tax assets, net operating losses carryforwards - state	19	20
Deferred tax assets, other	143	98
Subtotal deferred tax assets	831	723
Deferred tax assets, valuation allowances	(7)	(2)
Total deferred tax assets	824	721
Total deferred tax liabilities, net	2,310	2,188
IPL [Member]
Income Tax [Line Items]
Deferred tax liabilities, property	1,666	1,521
Deferred tax liabilities, other	112	120
Total deferred tax liabilities	1,778	1,641
Deferred tax assets, federal credit carryforwards	455	426
Deferred tax assets, net operating losses carryforwards - state	1	1
Deferred tax assets, other	48	37
Subtotal deferred tax assets	504	464
Deferred tax assets, valuation allowances	(4)	(2)
Total deferred tax assets	500	462
Total deferred tax liabilities, net	1,278	1,179
WPL [Member]
Income Tax [Line Items]
Deferred tax liabilities, property	1,060	999
Deferred tax liabilities, other	62	66
Total deferred tax liabilities	1,122	1,065
Deferred tax assets, federal credit carryforwards	199	166
Deferred tax assets, net operating losses carryforwards - state	0	0
Deferred tax assets, other	65	34
Subtotal deferred tax assets	264	200
Deferred tax assets, valuation allowances	(3)	0
Total deferred tax assets	261	200
Total deferred tax liabilities, net	861	865
ATC Holdings [Member]
Income Tax [Line Items]
Deferred tax liabilities, ATC Holdings	139	135
ATC Holdings [Member] | IPL [Member]
Income Tax [Line Items]
Deferred tax liabilities, ATC Holdings	0	0
ATC Holdings [Member] | WPL [Member]
Income Tax [Line Items]
Deferred tax liabilities, ATC Holdings	$ 0	$ 0