Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss), Beginning balance	$ (142)
Other comprehensive income	37	$ (8)	$ (89)
Accumulated other comprehensive income (loss), Ending balance	(105)	(142)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss), Beginning balance	(142)
Other comprehensive income	37	(8)	$ (89)
Accumulated other comprehensive income (loss), Ending balance	$ (105)	$ (142)