Summary of Significant Accounting Policies and Other Matters - Long-Lived and Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net	$ 1,290,000,000	$ 1,457,000,000
Accumulated amortization	297,000,000	228,000,000
Amortization of intangible assets	95,000,000	102,000,000	$ 99,000,000
Amortization expense, 2020	95,000,000
Amortization expense, 2021	95,000,000
Amortization expense, 2022	95,000,000
Amortization expense, 2023	95,000,000
Amortization expense, 2024	95,000,000
Impairment charges	0	0
Net non-utility plant	48,596,000,000	46,555,000,000
Intangible assets	1,293,000,000	1,460,000,000
Long-term debt	23,044,000,000	22,349,000,000
Power Purchase Agreements
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	288,000,000	220,000,000
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net	3,000,000	3,000,000
Accumulated amortization	$ 9,000,000	$ 8,000,000