Exit Activities and Discontinued Operations - Income from Discontinued Operations (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Oct. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale		$ 5	$ 0
Income tax expense		1	9
Income from discontinued operations, net of tax		4	34
Discontinued Operations, Held-for-sale | EnerBank
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenue		0	70
Operating expenses		0	15
Interest expense		0	12
Income before income taxes		0	43
Gain on sale	$ 657	5	0
Income from discontinued operations before income taxes		5	43
Income tax expense		1	9
Income from discontinued operations, net of tax		$ 4	$ 34