Income Taxes - Deferred Tax Assets and Liabilities, Net (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Deferred income taxes	$ 21	$ 59
Deferred income taxes (long-term liability)	(429)	(1,144)
Net Deferred Tax Assets (Liabilities)	$ (408)	$ (1,085)