CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (5,269)	$ (1,733)	$ 1,389
Items related to employee benefit plans:
Change in net actuarial gain (loss), net of $60, ($45) and ($60) tax	(195)	133	83
Change in net prior service credit, net of ($4), ($3) and ($4) tax	13	9	8
Unrealized holding loss on interest rate swaps, net of $12 tax	(39)	0	0
Foreign currency translation adjustment and other, net of ($6), $50 and ($17) tax	2	(201)	31
Net current-period other comprehensive income (loss)	(219)	(59)	122
COMPREHENSIVE (LOSS) INCOME	$ (5,488)	$ (1,792)	$ 1,511