Unrecognized Tax Benefits Reconciliation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at January 1	$ 11	$ 10
State decreases	0	(2)
Other increases	0	3
Balance at December 31	$ 11	$ 11