Special Charges (Credit) - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Income and Expenses [Abstract]
CARES Act grant	$ (1,494)	$ 0	$ (3,083)	$ 0
Severance and benefit costs	350	2	413	14
Impairment of assets	38	0	168	69
(Gains) losses on sale of assets and other special charges	25	25	35	33
Total operating special charges (credit)	(1,081)	27	(2,467)	116
Nonoperating special termination benefits and settlement losses	415	0	646	0
Nonoperating unrealized (gains) losses on investments		(21)	295	(72)
Nonoperating credit loss on BRW Term Loan and related guarantee	0	0	697	0
Total nonoperating special charges and unrealized (gains) losses on investments	400	(21)	1,638	(72)
Total operating and nonoperating special charges (credit) and unrealized (gains) losses on investments	(681)	6	(829)	44
Income tax expense (benefit), net of valuation allowance	148	(2)	375	(10)
Total operating and nonoperating special charges (credit) and unrealized (gains) losses on investments, net of income taxes	$ (533)	$ 4	$ (454)	$ 34