Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Intangible Assets By Major Class [Abstract]
Estimated weighted-average life (in years)	4 years 3 months 18 days
Amortization of Intangible Assets	$ 2	$ 4	$ 8