Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Allowance for credit losses	$ 39,000,000	$ 44,000,000
Accrued unbilled revenues, allowance for credit losses	2,000,000	6,000,000
Prepaid expenses and other current assets	100,000,000	132,000,000
Regulatory assets	$ 2,270,000,000	$ 2,321,000,000
Preferred Stock [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	20,000,000	20,000,000	20,000,000
Preferred stock, outstanding (in shares)	800,000	800,000
Preferred stock aggregate liquidation preference	$ 800	$ 800
Common Stock [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, authorized (in shares)	1,000,000,000	1,000,000,000	1,000,000,000
Common stock, outstanding (in shares)	629,432,406	628,923,534
Preferred stock	$ 790,000,000	$ 790,000,000
Variable Interest Entity, Primary Beneficiary
Prepaid expenses and other current assets	18,000,000	19,000,000
Regulatory assets	$ 372,000,000	$ 420,000,000