Supplemental Financial Information - Accrued Liabilities (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Dec. 31, 2020
Accrued Liabilities, Current [Abstract]
Extended Emergency Time Off		$ 190	$ 393
Voluntary Separation Program 2020		124	143
Profitsharing and savings plans		46	25
Vendor Prepayment	[1]	277	600
Vacation pay		443	436
Health		109	111
Workers compensation		163	161
Property and income taxes		80	84
Other		122	257
Accrued liabilities		1,665	2,259
Deferred revenue related to vendor prepayment		323
Accrued Liabilities [Member]
Accrued Liabilities, Current [Abstract]
Interest		$ 111	$ 49

[1] In fourth quarter 2020, the Company received a $600 million prepayment from Chase for Rapid Rewards points expected to be purchased during 2021, based on cardholder activity on the Visa credit card associated with its loyalty program. During first quarter 2021, $323 million was reclassified to deferred revenue in Air Traffic liability--loyalty (including $106 million that would have been a receivable from business partners as of March 31, 2021), and the remainder is expected to be reclassified during second quarter 2021.