Change in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 122,748	$ 111,732
Other comprehensive income (loss)	(5,183)	(2,793)
Balance	168,764	122,748
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(8,566)	(5,773)
Balance	(13,749)	(8,566)
Unrealized Gain (Loss) on Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(11)	(33)
Other comprehensive income (loss)	6	22
Balance	(5)	(11)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(8,555)	(5,740)
Other comprehensive income (loss)	(5,189)	(2,815)
Balance	$ (13,744)	$ (8,555)