Contingencies - Antitrust Litigation and Investigations (Details) - USD ($)	1 Months Ended			3 Months Ended
	Apr. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2016	Nov. 30, 2017
Loss Contingencies [Line Items]
Percentage of bookings affected (fraction of)							1.00%
Value added tax receivable					$ 22,000,000
Foreign Tax Authority | Indian Income Tax Litigation
Loss Contingencies [Line Items]
Termination fee					45,000,000
US Airways Litigation
Loss Contingencies [Line Items]
Damages awarded	$ 15,000,000					$ 15,000,000
Loss contingency accrual			$ 32,000,000		0	32,000,000
Reasonable attorneys' fees, expenses and costs						$ 17,000,000
Department Of Justice Lawsuit
Loss Contingencies [Line Items]
Litigation charge					46,000,000
Termination fees					$ 21,000,000
Department Of Justice Lawsuit | Subsequent Event
Loss Contingencies [Line Items]
Termination fees				$ 21,000,000
US Airways | US Airways Litigation
Loss Contingencies [Line Items]
Damages awarded		$ 15,000,000	$ 5,000,000
Attorneys' fees and costs sought		$ 125,000,000