CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (37)	$ 152	$ (258)	$ 487
Net change in unrealized gains (losses), net of tax, on:
Derivatives designated as cash flow hedges	8	11	28	34
Pension and postretirement benefit plan adjustments	0	1	0	1
Other comprehensive income, net of tax	8	12	28	35
Total comprehensive income (loss)	$ (29)	$ 164	$ (230)	$ 522