Segment Reporting - Schedule of Revenue by Geographic Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total	$ 60,687	$ 57,801	$ 117,370	$ 110,266
% of Total	100.00%	100.00%	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Total	$ 27,086	$ 26,750	$ 51,971	$ 46,680
% of Total	44.60%	46.30%	44.30%	42.30%
Japan [Member]
Segment Reporting Information [Line Items]
Total	$ 11,718	$ 14,854	$ 23,370	$ 29,315
% of Total	19.30%	25.70%	19.90%	26.60%
Europe Middle East Africa [Member]
Segment Reporting Information [Line Items]
Total	$ 15,060	$ 12,551	$ 30,064	$ 23,440
% of Total	24.80%	21.70%	25.60%	21.30%
Rest of the World [Member]
Segment Reporting Information [Line Items]
Total	$ 6,823	$ 3,646	$ 11,965	$ 10,831
% of Total	11.30%	6.30%	10.20%	9.80%