Regulatory Matters (Assets Retired Early) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets	$ 1,940	$ 2,010
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	92	113
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,443	1,483
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	77
IPL [Member] | Assets retired early [Member] | Sutherland Units 1 and 3 [Member]
Regulatory Assets [Line Items]
Regulatory assets	19
IPL [Member] | Assets retired early [Member] | M.L. Kapp Unit 2 [Member]
Regulatory Assets [Line Items]
Regulatory assets	18
IPL [Member] | Assets retired early [Member] | Analog Electric Meters [Member]
Regulatory Assets [Line Items]
Regulatory assets	29
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	497	527
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	26	$ 36
WPL [Member] | Assets retired early [Member] | Nelson Dewey Units 1 and 2 and Edgewater Unit 3 [Member]
Regulatory Assets [Line Items]
Regulatory assets	6
WPL [Member] | Assets retired early [Member] | Edgewater Unit 4 [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 20