Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020
Accumulated other comprehensive income (loss), Beginning balance			$ (128)				$ (128)
Other comprehensive income (loss)	$ 3	$ 8	(39)	$ (11)	$ 1	$ 10
Accumulated other comprehensive income (loss), Ending balance	(156)						(156)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss), Beginning balance			(128)				(128)
Other comprehensive income (loss)	3	$ 8	$ (39)	$ (11)	$ 1	$ 10	(28)
Accumulated other comprehensive income (loss), Ending balance	$ (156)						$ (156)