Segment Reporting - Schedule of Revenue by Geographic Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Total	$ 56,683	$ 52,465
% of Total	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Total	$ 24,823	$ 23,597
% of Total	43.80%	45.00%
Japan [Member]
Segment Reporting Information [Line Items]
Total	$ 11,652	$ 14,461
% of Total	20.50%	27.60%
Europe Middle East Africa [Member]
Segment Reporting Information [Line Items]
Total	$ 15,066	$ 10,860
% of Total	26.60%	20.70%
Rest of the World [Member]
Segment Reporting Information [Line Items]
Total	$ 5,142	$ 3,547
% of Total	9.10%	6.70%