CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 15	$ (134)	$ 437	$ (208)
Net change in unrealized gains (losses), net of tax, on:
Fair value option debt attributable to credit spread	0	0	(5)	0
Derivatives designated as cash flow hedges	0	7	0	15
Pension and postretirement benefit plan adjustments	(9)	(2)	(10)	(3)
Other comprehensive income (loss), net of tax	(9)	5	(15)	12
Total comprehensive income (loss)	$ 6	$ (129)	$ 422	$ (196)