CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 865	$ (189)	$ 2,894
Defined benefit plans:
Actuarial gains (losses) arising during the period, net of taxes	46	(116)	(77)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	0	0	4
Amortization or curtailment of unrecognized amounts included in net periodic benefit costs	45	47	48
Foreign exchange (losses) gains	(1)	1	(1)
Other comprehensive income (loss)	90	(68)	(34)
Total comprehensive income (loss)	955	(257)	2,860
Total comprehensive income attributable to noncontrolling interests	(263)	(53)	(291)
Total comprehensive income (loss) attributable to common stockholders	$ 692	$ (310)	$ 2,569