Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Regulatory Matters [Line Items]
Regulatory assets	$ 2,269	$ 2,046
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	1,590	1,386
WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	679	660
Assets retired early [Member]
Regulatory Matters [Line Items]
Regulatory assets	282	70
Assets retired early [Member] | IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	267	53
Assets retired early [Member] | WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	15	$ 17
Assets retired early [Member] | Lansing Generating Station
Regulatory Matters [Line Items]
Regulatory assets	221
Assets retired early [Member] | Lansing Generating Station | IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	$ 221