Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Line Items]
Net deferred tax asset	$ 20,233	$ 28,571
Change in net deferred tax asset position	8,300
Deferred tax asset reduction U.S. corporate tax rate	7,200
Repatriation of accumulated untaxed earnings of foreign subsidiaries	4,000
Valuation allowance	15,021	12,546
Cash held by foreign subsidiaries	38,200
Unrecognized tax benefits liability	485	628	$ 489	$ 27
Accrued interest and penalties are included in the unrecognized tax benefits	$ 300	$ 200
Minimum
Income Tax Disclosure [Line Items]
Federal research and development tax credit carryforward expiration year	2026
Maximum
Income Tax Disclosure [Line Items]
Federal research and development tax credit carryforward expiration year	2038
Research And Development
Income Tax Disclosure [Line Items]
Tax credits carried forward	$ 1,600
Foreign Tax Authority
Income Tax Disclosure [Line Items]
Release of valuation allowance	2,300
Net operating loss carryforwards	71,500
Domestic Tax Authority
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	24,000
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Valuation allowance	200
Net operating loss carryforwards	$ 65,600