Goodwill and Acquired Intangible Assets - Aggregate Amortization Expense for Acquired Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 11	$ 12	$ 22	$ 23
Amortization expense - Remainder of 2015	42		42
Amortization expense - 2016	33		33
Amortization expense - 2017	25		25
Amortization expense - 2018	14		14
Amortization expense - 2019	11		11
Amortization expense - 2020	$ 5		$ 5