Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period			$ 43,392
Balance at end of period	$ 35,251		35,251
Foreign currency translation
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(1,078)	$ (1,250)	(1,574)	$ (1,568)
Total other comprehensive (loss) income	190	57	686	375
Balance at end of period	(888)	(1,193)	(888)	(1,193)
Available-for-sale marketable securities
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	7	4	6	12
Other comprehensive (loss) income	(2)	4	(1)	(4)
Balance at end of period	5	8	5	8
Total accumulated other comprehensive loss
Increase (Decrease) in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at end of period	$ (883)	$ (1,185)	$ (883)	$ (1,185)