Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 245	$ 286	$ 886	$ (4,225)
Other comprehensive (loss) income, net of taxes:
Unrealized gains on securities	0	2	2	3
Defined benefit plans:
Defined Benefit Plan, Gain (Loss), Actuarial Gain, Net of Tax	0	0	69	0
Amortization or curtailment of unrecognized amounts included in net periodic benefit costs	12	11	42	34
Foreign exchange gains (losses)	1	(1)	0	(11)
Defined Benefit Plan, Gain (Loss), Actuarial Gain, Tax	0		48
Other comprehensive income	13	12	113	26
Total comprehensive income (loss)	258	298	999	(4,199)
Total comprehensive loss (income) attributable to noncontrolling interests	35	(59)	(118)	(189)
Preferred dividends attributable to redeemable noncontrolling interest	0	(10)	0	(31)
Total comprehensive income (loss)	$ 293	$ 229	$ 881	$ (4,419)