Special Charges (Credits) and Unrealized (Gains) Losses on Investments - Components of Special Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating:
CARES Act grant	$ (4,021)	$ (3,536)	$ 0
Severance and benefit costs	438	575	16
Impairment of assets	97	318	171
(Gains) losses on sale of assets and other special charges	119	27	59
Total operating special charges (credits)	(3,367)	(2,616)	246
Nonoperating unrealized (gains) losses on investments, net	34	194	(153)
Nonoperating debt extinguishment and modification fees	50	0	0
Nonoperating special termination benefits and settlement losses	31	687	0
Nonoperating credit loss on BRW Term Loan and related guarantee	0	697	0
Total nonoperating special charges and unrealized (gains) losses on investments, net	115	1,578	(153)
Total operating and nonoperating special charges (credits) and unrealized (gains) losses on investments, net	(3,252)	(1,038)	93
Income tax expense (benefit), net of valuation allowance	728	404	(21)
Total operating and nonoperating special charges (credits) and unrealized (gains) losses on investments, net of income taxes	$ (2,524)	$ (634)	$ 72