Difference Between Provision for Income Taxes and Amounts Computed by Applying Federal Statutory Income Tax Rate to Loss before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Federal statutory tax	$ (8,891)	$ (11,352)	$ (12,510)
Federal research credits	1,874	(2,159)	(1,630)
State research credits	(822)	(767)	(749)
Expiration of federal carryovers	4,858	4,651	9,200
Change in valuation allowance	6,379	10,482	6,738
Compensation related items	1,794	460	978
State taxes	(1,127)	(1,294)	(1,921)
Other	171	298	178
Provision for income taxes	$ 488	$ 319	$ 284

Income tax reconciliation, expiration of federal net operating losses.

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Income tax reconciliation state tax credits research.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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