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Asset Impairments (Details) - USD ($) $ in Millions	3 Months Ended						12 Months Ended
Asset Impairments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Asset Impairments
Impairment losses							$ 35
Impairment losses, other assets									$ 12
Petra Nova Parish Holdings
Asset Impairments
Impairment losses on equity method investments					$ 18	$ 101
Letter of credit						12
Contribution in cash						95
Guarantee (up to)						$ 124
East
Asset Impairments
Impairment	$ 16
Impairment losses							35
East \| Joliet facility
Asset Impairments
Impairment	213
East \| PJM Coal Generating Assets
Asset Impairments
Impairment		$ 271
Impairment losses		$ 35
West/Services/Other
Asset Impairments
Impairment	$ 9
West/Services/Other \| Held-for-sale \| Home Solar
Asset Impairments
Impairment loss to adjust the carrying amount of assets and liabilities			$ 29	$ 29
West/Services/Other \| Cottonwood
Asset Impairments
Impairment losses on equity method investments							32
Texas
Asset Impairments
Impairment losses							$ 0
Impairment losses, other assets								$ 14