Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill deductible for income tax purposes	$ 67		$ 67
Amortization expense, intangible assets	116	$ 109	227	$ 210
Amortization expense, computer software	$ 64	$ 60	$ 126	$ 113