Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Components Of Deferred Tax Assets And Liabilities [Line Items]
Operating loss carryforwards	$ 39,982	$ 36,417
Tax credit carryforwards	910	1,195
Other temporary differences	5,278	4,678
Deferred Tax Assets, Gross, Total	46,170	42,290
Less valuation allowance	(46,170)	(42,290)
Net deferred tax asset	$ 0	$ 0