Common Stockholders' Equity and Preferred Securities - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Mar. 03, 2021	Jun. 15, 2020
Class of Stock [Line Items]
Warrants issued	$ 99	$ 97
Proceeds from the issuance of common stock		$ 1,100
Common stock reserved for future issuance (in shares)	6,000,000
Junior preferred stock outstanding (in shares)	2
Junior preferred stock par value per share (in dollars per share)	$ 0.01
Preferred stock authorized to issue (in shares)	250,000,000
2020 ATM Offering
Class of Stock [Line Items]
Sale of common stock (in shares)		21,000,000
Share price (in dollars per share)		$ 46.70
Proceeds from the issuance of common stock		$ 989
Public Offering
Class of Stock [Line Items]
Sale of common stock (in shares)		43,000,000
Share price (in dollars per share)		$ 26.50
Equity Distribution Agreement
Class of Stock [Line Items]
Sale of common stock (in shares)	7,000,000
Share price (in dollars per share)	$ 42.98
Proceeds from the issuance of common stock	$ 282
Number of shares issuable under Equity Distribution Agreement (up to) (in shares)				28,000,000
2021 ATM Offering
Class of Stock [Line Items]
Sale of common stock (in shares)	4,000,000
Share price (in dollars per share)	$ 57.50
Proceeds from the issuance of common stock	$ 250
Number of shares issuable under Equity Distribution Agreement (up to) (in shares)			37,000,000
Payroll Support Program 2 & 3 (PSP 2 & 3) Warrants
Class of Stock [Line Items]
Number of warrants issuable under agreement (up to)	3,500,000
Warrants issued	$ 99