Common Stockholders' Equity and Preferred Securities - Summary of Warrants Outstanding (Details) - USD ($) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Number of shares of common stock (in shares)	10.0
Unsecured Debt | PSP2 Note
Class of Warrant or Right [Line Items]
Aggregate principal amount	$ 870,000,000
Term of debt	10 years
Unsecured Debt | Payroll Support Program 1 (PSP1) Note
Class of Warrant or Right [Line Items]
Aggregate principal amount	$ 1,500,000,000
Term of debt	10 years
Line of Credit | CARES Act Credit Agreement
Class of Warrant or Right [Line Items]
Aggregate principal amount		$ 520,000,000
PSP1 Warrants
Class of Warrant or Right [Line Items]
Number of shares of common stock (in shares)	4.8
Exercise price (in dollars per share)	$ 31.50
CARES Act Loan Warrants
Class of Warrant or Right [Line Items]
Number of shares of common stock (in shares)	1.7
Exercise price (in dollars per share)	$ 31.50
PSP2 Warrants
Class of Warrant or Right [Line Items]
Number of shares of common stock (in shares)	2.0
Exercise price (in dollars per share)	$ 43.26
PSP3 Warrants
Class of Warrant or Right [Line Items]
Number of shares of common stock (in shares)	1.5
Exercise price (in dollars per share)	$ 53.92