CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (529)	$ (431)	$ 523
Net change in unrealized gains (losses), net of tax, on:
Derivatives designated as cash flow hedges	15	37	45
Pension and postretirement benefit plan adjustments	(5)	42	(2)
Other comprehensive income, net of tax	10	79	43
Total comprehensive income (loss)	$ (519)	$ (352)	$ 566