Special Charges (Credit) - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Income and Expenses [Abstract]
CARES Act grant	$ (1,589)	$ 0	$ (1,589)	$ 0
Impairment of assets	80	61	130	69
Severance and benefit costs	63	6	63	12
(Gains) losses on sale of assets and other special charges	(3)	4	10	8
Total operating special charges (credit)	(1,449)	71	(1,386)	89
Nonoperating special termination benefits and settlement losses	231	0	231	0
Nonoperating unrealized (gains) losses on investments	(9)	(34)	310	(51)
Nonoperating credit loss on BRW Term Loan and related guarantee	0	0	697	0
Total nonoperating special charges (credit) and unrealized (gains) losses on investments	222	(34)	1,238	(51)
Total operating and nonoperating special charges (credit) and unrealized (gains) losses on investments	(1,227)	37	(148)	38
Income tax expense (benefit), net of valuation allowance	241	(8)	227	(8)
Total operating and nonoperating special charges (credit) and unrealized (gains) losses on investments, net of income taxes	$ (986)	$ 29	$ 79	$ 30