Special Charges (Credits) - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Other Income and Expenses [Abstract]
CARES Act grant	$ 0	$ (1,810)
Severance and benefit costs	0	417
(Gains) losses on sale of assets and other special charges	(8)	16
Total operating special charges (credits)	(8)	(1,377)
Nonoperating unrealized losses on investments, net	0	22
Nonoperating debt extinguishment fees	7	0
Nonoperating special termination benefits	0	46
Total nonoperating special charges and unrealized losses on investments, net	7	68
Total operating and nonoperating special charges (credits) and unrealized losses on investments, net	(1)	(1,309)
Income tax expense, net of valuation allowance	0	291
Total operating and nonoperating special charges (credits) and unrealized losses on investments, net of income taxes	$ (1)	$ (1,018)