Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Basis difference in equipment	$ (438)	$ (459)
Basis difference in intangibles	(5,356)	(6,045)
Accrued liabilities and other	3,942	2,246
R&D credit	10,980	10,980
Stock options	4,416	4,360
Net operating loss carry-forward	62,535	64,376
Gross, Deferred Tax Assets	76,079	75,458
Less: valuation allowance	(76,079)	(75,458)
Net of Valuation Allowance	$ 0	$ 0

Deferred tax assets tax deferred expense reserves and accruals accrued liabilities and other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets including goodwill.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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