Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Intangible Assets by Major Class
Estimated weighted-average life (in years)			4 years 4 months 24 days
Amortization of Intangible Assets	$ 1	$ 2	$ 3	$ 6