Significant Items Making up Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Components Of Deferred Tax Assets And Liabilities [Abstract]
Allowances not currently deductible for tax purposes	$ 451	$ 433
Net operating loss carryforwards	45,196	48,860
Operating lease liabilities	513	1,135
General carryforwards	16,242	13,366
Stock options	1,291	1,229
Accrued and other	1,990	1,900
Deferred Tax Assets, Gross, Total	65,683	66,923
Less valuation allowance	(62,699)	(62,492)
Deferred Tax Assets, Net of Valuation Allowance, Total	2,984	4,431
Depreciation and amortization	(1,032)	(1,556)
Operating lease right-of-use assets	(169)	(1,086)
State income taxes	(1,783)	(1,789)
Deferred Tax Liabilities, Gross, Total	$ (2,984)	$ (4,431)