Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 14	$ (17)	$ 16	$ (40)
Other comprehensive income (loss):
Foreign currency translation adjustments	(20)	12	(19)	22
Comprehensive loss	$ (6)	$ (5)	$ (3)	$ (18)