Intangible Assets - Amortization Expense Charged to Income for 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	$ 93	$ 86	$ 179	$ 169