Income Taxes - Reconciliation Between Income Tax Provision (Benefit) Computed at Federal Statutory Rate and Actual Tax Provision (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax provision at federal statutory rate	$ 4,246	$ 13,527	$ 12,449
State income taxes, net of federal benefit	(1,426)	62	800
Research and development credits	(1,508)	(2,627)	(4,217)
Effect of foreign operations	(1,344)	(3,320)	(3,412)
Deemed repatriation transition tax	16,976
Provision for remeasuring deferred tax balances	10,450
Reduction in accrual for estimated potential tax assessments	(1,676)	(15,404)	(4,808)
Non-deductible stock-based compensation pursuant to ASC 718-740	1,249	1,288	3,244
Domestic manufacturing deduction		(831)	(878)
Meals and entertainment	500	475	474
Other	8	529	(283)
Provision for (benefit from) income taxes	$ 27,475	$ (6,301)	$ 3,369
Tax provision at federal statutory rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	(11.80%)	0.20%	2.20%
Research and development credits	(12.40%)	(6.80%)	(11.90%)
Effect of foreign operations	(11.10%)	(8.50%)	(9.50%)
Deemed repatriation transition tax	139.80%
Provision for remeasuring deferred tax balances	86.10%
Reduction in accrual for estimated potential tax assessments	(13.70%)	(39.90%)	(13.40%)
Non-deductible stock-based compensation pursuant to ASC 718-740	10.30%	3.30%	9.10%
Domestic manufacturing deduction		(2.20%)	(2.50%)
Meals and entertainment	4.10%	1.20%	1.30%
Other	0.10%	1.40%	(0.80%)
Provision for (benefit from) income taxes	226.40%	(16.30%)	9.50%