Special Charges (Credits) - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other Income and Expenses [Abstract]
CARES Act grant	$ (1,810)	$ 0
Severance and benefit costs	417	0
Impairment of assets	0	50
(Gains) losses on sale of assets and other special charges	16	13
Total operating special charges (credits)	(1,377)	63
Nonoperating special termination benefits	46	0
Nonoperating unrealized losses on investments, net	22	319
Nonoperating credit loss on BRW Term Loan and related guarantee	0	697
Total nonoperating special charges and unrealized losses on investments, net	68	1,016
Total operating and nonoperating special charges (credits) and unrealized losses on investments, net	(1,309)	1,079
Income tax expense (benefit), net of valuation allowance	291	(14)
Total operating and nonoperating special charges (credits) and unrealized losses on investments, net of income taxes	$ (1,018)	$ 1,065