Significant Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Operating loss carryforward		$ 13,069	$ 9,638
Accrued expenses and deferred revenues		1,057	1,128
Temporary differences related to R&D expenses		2,118	1,435
Equity-based compensation		1,956	2,685
Tax credit carry forward		1,866	1,237
Other		476	562
Total gross deferred tax assets		20,542	16,685
Valuation allowance		(16,590)	(13,780)
Net deferred tax assets		3,952	2,905
Deferred tax liabilities
Intangible assets		275	621
Other		34	32
Total deferred tax liabilities		309	653
Net deferred tax assets	[1]	$ 3,643	$ 2,252

[1] Net deferred taxes for the years ended December 31, 2016 and 2017 are all from foreign jurisdictions.