Commitments and Contingengies - Long-term Purchase Commitments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) aircraft
Long-term Purchase Commitment
Number of Aircraft Grounded Under Emergency Order	34
Aircraft
Long-term Purchase Commitment
Committed expenditures, 2020	$ 2,100
Committed expenditures, 2021	1,700
Committed expenditures, 2022	1,200
Committed expenditures, 2023	1,600
Committed expenditures, 2024	1,900
Committed expenditures, 2025 and beyond	$ 1,500
B-737-8 Max
Long-term Purchase Commitment
Property, Plant and Equipment, Number of Aircraft Purchased | aircraft	3
B-737-8 Max
Long-term Purchase Commitment
Long-term Purchase Commitment, Minimum Quantity Required | aircraft	219
Options - 737MAX (in units) | aircraft	115
B-737-7 Max
Long-term Purchase Commitment
Long-term Purchase Commitment, Minimum Quantity Required | aircraft	30