Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (52)	$ (234)	$ (502)
Other comprehensive income (loss):
Foreign currency translation adjustments	37	(8)	(89)
Comprehensive loss	$ (15)	$ (242)	$ (591)