Exit Activities and Discontinued Operations - Income from Discontinued Operations (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Oct. 31, 2021	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense										$ 170	$ 18	$ 16
Income from discontinued operations, net of tax		$ 520	$ 30	$ 18	$ 34	$ 24	$ 12	$ 8	$ 14	602	58	49
Discontinued Operations, Held-for-sale | EnerBank
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenue										209	262	221
Operating expenses										60	130	97
Interest expense										34	56	59
Income before income taxes										115	76	65
Gain on sale	$ 657									657	0	0
Income from discontinued operations before income taxes										772	76	65
Income tax expense										170	18	16
Income from discontinued operations, net of tax										$ 602	$ 58	$ 49