Reconciliation of Federal Statutory Rate to Effective Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Rate Reconciliation [Line Items]
Income before income taxes	$ 59,217	$ 26,151	$ 21,436
Expected tax at statutory rate	12,436	5,492	4,502
Adjustments due to:
Difference between U.S. and foreign tax	618	436	345
State income and franchise tax	133	(179)	91
Business tax credits	(4,660)	(2,746)	(1,760)
Stock-based compensation expense	(9,243)	(1,877)	(1,213)
U.S. taxation of foreign earnings	51	2,227	2,190
Executive compensation	1,401	841	367
Other	896	92	97
Change in U.S. federal tax rates	(2,192)
Change in U.S. state tax rates	(708)		748
Change in Netherlands tax rate	250	(193)	(388)
Transition tax			(1,338)
Uncertain tax provisions	(168)	1,069	1,021
Change in valuation allowance	(12)	(125)	125
Return to provision adjustments	(89)	(79)	33
Other	578	(218)	(1)
Income tax (benefit) provision	$ (709)	$ 4,740	$ 4,819
Expected tax at statutory rate	21.00%	21.00%	21.00%
Adjustments due to:
Difference between U.S. and foreign tax	1.00%	1.70%	1.60%
State income and franchise tax	0.20%	(0.70%)	0.40%
Business tax credits	(7.90%)	(10.50%)	(8.20%)
Stock-based compensation expense	(15.60%)	(7.20%)	(5.70%)
U.S. taxation of foreign earnings	0.10%	8.50%	10.20%
Executive compensation	2.40%	3.20%	1.70%
Other	1.50%	0.40%	0.50%
Change in U.S. federal tax rates	(3.70%)	0.00%	0.00%
Change in U.S. state tax rates	(1.20%)	0.00%	3.50%
Change in Netherlands tax rate	0.40%	(0.70%)	(1.80%)
Transition tax	0.00%	0.00%	(6.20%)
Uncertain tax provisions	(0.30%)	4.10%	4.80%
Change in valuation allowance	0.00%	(0.50%)	0.60%
Return to provision adjustments	(0.20%)	(0.30%)	0.20%
Other	1.00%	(0.80%)	(0.10%)
Income tax (benefit) provision	(1.20%)	18.10%	22.50%