Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. Federal tax benefit at statutory rates	$ (3,130)	$ (310)
Impact of:
Tax credits	(376)	(170)
State income tax	(1)	25
International operations	168	183
Stock-based compensation	(130)	(23)
Valuation allowance	(5,688)	311
Expiration of state net operating loss carryforwards		77
Impact of tax reform	8,929
Other, net	79	48
Total Income tax expense (benefit)	$ (149)	$ 141
U.S. Federal tax benefit at statutory rates	34.00%	34.00%
Impact of:
Tax credits	4.10%	18.60%
State income tax	0.00%	(2.70%)
International operations	(1.80%)	(20.10%)
Stock-based compensation	1.40%	2.60%
Valuation allowance	61.80%	(34.20%)
Expiration of state net operating loss carryforwards		(8.50%)
Impact of tax reform	(97.00%)
Other, net	(0.90%)	(5.40%)
Tax expense (benefit) and effective tax rate	1.60%	(15.70%)