Intangible Assets - Amortization Expense Charged to Income for Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense	$ 156	$ 88	$ 405	$ 267