Income Taxes - Reconciliation of the Company's Effective Income Tax Rate to the Federal Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal income tax at the statutory rate	$ 5,902	$ 5,518	$ 11,024
State income taxes, net of federal benefit	(215)	339	889
Difference between statutory and foreign tax rates	7	(560)	1,521
Permanent differences	725	300	(457)
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	1,167	0	0
Research and development	(6,908)	(2,380)	(1,928)
Return to provision adjustment	1,780	23	327
Change in liability for unrecognized tax benefits	1,768	7	700
Excess stock-based compensation benefit	(8,907)	(1,819)	(77)
Change in valuation allowance	1,984	1,949	1,779
Tax effects of intercompany transactions	(1,004)	277	(630)
Adjustments to deferreds resulting from enactment of new tax law	0	7,601	0
Other	592	(147)	(208)
Provision for income taxes	$ (1,101)	$ 10,554	$ 14,200
Effective tax rate	(3.90%)	66.90%	45.10%
Excess tax benefit from stock-based compensation			$ 1,438