Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (19)	$ (48)	$ (46)	$ (63)
Cash flow hedge adjustment, net of tax		3		3
Termination of cash flow hedge		(3)		(3)
Comprehensive net loss	$ (19)	$ (48)	$ (46)	$ (63)