Special Charges (Credits) - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Income and Expenses [Abstract]
CARES Act grant	$ (1,079)	$ (1,589)	$ (2,889)	$ (1,589)
Impairment of assets	59	80	59	130
Severance and benefit costs	11	63	428	63
(Gains) losses on sale of assets and other special charges	61	(3)	77	10
Total operating special charges (credits)	(948)	(1,449)	(2,325)	(1,386)
Nonoperating unrealized (gains) losses on investments, net	(147)	(9)	(125)	310
Nonoperating debt extinguishment and modification fees	62	0	62	0
Settlement loss — Voluntary Programs (defined below)	0	231	46	231
Nonoperating credit loss on BRW Term Loan and related guarantee	0	0	0	697
Total nonoperating special charges and unrealized (gains) losses on investments, net	(85)	222	(17)	1,238
Total operating and nonoperating special charges (credits) and unrealized (gains) losses on investments, net	(1,033)	(1,227)	(2,342)	(148)
Income tax expense (benefit), net of valuation allowance	203	241	494	227
Total operating and nonoperating special charges (credits) and unrealized (gains) losses on investments, net of income taxes	$ (830)	$ (986)	$ (1,848)	$ 79