CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (189)	$ 2,894	$ 2,095
Other comprehensive income (loss), net of taxes:
Unrealized gains on securities	0	0	1
Defined benefit plans:
Actuarial (losses) gains arising during the period, net of taxes	(116)	(77)	14
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	0	4	0
Amortization or curtailment of unrecognized amounts included in net periodic benefit costs	47	48	54
Foreign exchange gains (losses)	1	(1)	0
Other comprehensive (loss) income	(68)	(34)	69
Total comprehensive (loss) income	(257)	2,860	2,164
Total comprehensive income attributable to noncontrolling interests	(53)	(291)	(286)
Total comprehensive (loss) income attributable to common stockholders	$ (310)	$ 2,569	$ 1,878