Benefit Plans (Amounts Recognized On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	$ (511)	$ (484)
Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	(2)	(14)
Pension and other benefit obligations	(365)	(335)
Net amounts recognized at December 31	(367)	(349)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	533	485
Prior service credit	(5)	(5)
Net amount recognized at December 31	528	480
Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	8	10
Current liabilities	(8)	(8)
Pension and other benefit obligations	(119)	(111)
Net amounts recognized at December 31	(119)	(109)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	54	45
Prior service credit	(1)	(1)
Net amount recognized at December 31	53	44
IPL [Member]
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	(186)	(168)
IPL [Member] | Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	(1)	(1)
Pension and other benefit obligations	(161)	(144)
Net amounts recognized at December 31	(162)	(145)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	228	208
Prior service credit	(1)	(1)
Net amount recognized at December 31	227	207
IPL [Member] | Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	4	7
Current liabilities	(2)	(2)
Pension and other benefit obligations	(19)	(19)
Net amounts recognized at December 31	(17)	(14)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	20	17
Prior service credit	0	0
Net amount recognized at December 31	20	17
WPL [Member]
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	(222)	(211)
WPL [Member] | Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	0	0
Pension and other benefit obligations	(152)	(144)
Net amounts recognized at December 31	(152)	(144)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	233	212
Prior service credit	(1)	(1)
Net amount recognized at December 31	232	211
WPL [Member] | Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	3	3
Current liabilities	(6)	(6)
Pension and other benefit obligations	(68)	(65)
Net amounts recognized at December 31	(71)	(68)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	25	22
Prior service credit	(1)	(1)
Net amount recognized at December 31	$ 24	$ 21