Boeing 737 MAX Aircraft Grounding (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) aircraft	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of Aircraft Grounded Under Emergency Order on March 13, 2019	34
After-Tax Potential Concessions and Other Considerations Announced July 2019 | $	$ 4,900
Pre-Tax Potential Concessions and Other Considerations Announced January 2020 | $	$ 2,600
Number of Aircraft Not Delivered Due to Grounding Under Emergency Order	41
Supplier Proceeds | $	$ 428	$ 400	$ 0
Contract to Own Aircraft
Number of Aircraft Not Delivered Due to Grounding Under Emergency Order	28
Contract to Lease Aircraft
Number of Aircraft Not Delivered Due to Grounding Under Emergency Order	13
737 MAX 8
Property, Plant and Equipment, Number of Aircraft Leased	7