Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. Federal tax benefit at statutory rates	$ (2,889)	$ (3,130)
Impact of:
Tax credits	(517)	(376)
State income tax	10	(1)
International operations	30	168
Stock-based compensation	2	(130)
Valuation allowance	2,280	(5,688)
Expiration of tax attributes	217
Impact of tax reform		8,929
Goodwill impairment	784
Other, net	96	79
Total Income tax expense (benefit)	$ 13	$ (149)
U.S. Federal tax benefit at statutory rates	21.00%	34.00%
Impact of:
Tax credits	3.80%	4.10%
State income tax	(0.10%)	0.00%
International operations	(0.20%)	(1.80%)
Stock-based compensation		1.40%
Valuation allowance	(16.60%)	61.80%
Expiration of tax attributes	(1.60%)
Impact of tax reform		(97.00%)
Goodwill impairment	(5.70%)
Other, net	(0.70%)	(0.90%)
Tax expense (benefit) and effective tax rate	(0.10%)	1.60%