Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 20	$ (9)	$ 36	$ (49)
Other comprehensive income (loss):
Foreign currency translation adjustments	4	16	(15)	38
Comprehensive income (loss)	$ 24	$ 7	$ 21	$ (11)