Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Beginning Balance	$ 63	$ 63	$ 54
Additions based on tax positions related to the current year	6	5	4
Additions for tax positions for prior years	3	5	9
Reductions for tax positions for prior years	(14)	(8)	0
Settlements	(1)	(2)	0
Statute of limitations	(1)	0	(4)
Ending Balance	$ 56	$ 63	$ 63