Income Taxes - Reconciliation of Unrecognized Tax Benefits (Excluding Interest and Penalties) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 28	$ 18	$ 7
Additions for tax positions of the current year	23	12	0
Additions for tax positions of prior years	27	0	14
Reductions for tax positions of prior years	0	0	(2)
Settlements with tax authorities	0	(1)	0
Expiration of the statute of limitations	(5)	(1)	(1)
Foreign currency translation	0	0	0
Balance at end of year	$ 73	$ 28	$ 18