Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax		$ 48		$ 48
Net income	$ 1,035	335	$ 1,852	641
Other comprehensive (loss) income, net of taxes:
Unrealized gains on securities	0	1	0	2
Defined benefit plans:
Actuarial gains arising during the period, net of taxes of $48 million for the three and six months ended June 30, 2017	0	69	0	69
Amortization of unrecognized amounts included in net periodic benefit costs	11	19	23	30
Foreign exchange losses	0	0	(1)	(1)
Other comprehensive income	11	89	22	100
Total comprehensive income	1,046	424	1,874	741
Total comprehensive income attributable to noncontrolling interests	(166)	(75)	(290)	(153)
Total comprehensive income (loss)	$ 880	$ 349	$ 1,584	$ 588