Reconciliation of Gross Uncertain Tax Positions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Amount established upon adoption	$ 1,200	$ 1,200	$ 1,200
Additions for current year tax provisions	0	0	0
Additions for prior year tax provisions	0	0	0
Reductions of prior year tax provisions	0	0	0
Balance as of end of year	$ 1,200	$ 1,200	$ 1,200