Accumulated Other Comprehensive Income (Loss) - Schedule of Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ (7,573)
Foreign currency translation	$ 2,514	$ (1,429)	3,304	$ 52
Unrealized gain on investments, net of tax	7	3	24	120
Ending Balance	(4,245)		(4,245)
Beginning Balance			150,036
Ending Balance	127,374		127,374
Net Unrealized Gain (Loss) on Marketable Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(66)	17	(83)	(100)
Unrealized gain on investments, net of tax	7	3	24	120
Ending Balance	(59)	20	(59)	20
Cumulative Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,700)	(3,245)	(7,490)	(4,726)
Foreign currency translation	2,514	(1,429)	3,304	52
Ending Balance	(4,186)	(4,674)	(4,186)	(4,674)
Total Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,766)	(3,228)	(7,573)	(4,826)
Ending Balance	$ (4,245)	$ (4,654)	$ (4,245)	$ (4,654)