Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Amortization of Intangible Assets	$ 245	$ 386	$ 430
Impairment of Intangible Assets	0		0
Goodwill accumulated impairment	0	0
Goodwill impairment loss	$ 0	0	$ 0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		$ 17