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
Consolidated Statements Of Comprehensive Income (Loss) [Abstract]
Net income (loss)	$ (18)	$ (662)	$ 2	$ (737)
Other comprehensive income (loss), net of tax	71	(3)	70	58
Comprehensive income (loss)	$ 53	$ (665)	$ 72	$ (679)