Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Beginning Balance	$ 56	$ 63	$ 63
Additions based on tax positions related to the current year	3	6	5
Additions for tax positions for prior years	3	3	5
Reductions for tax positions for prior years	(3)	(14)	(8)
Settlements	0	(1)	(2)
Statute of limitations	0	(1)	0
Ending Balance	$ 59	$ 56	$ 63