Income Taxes - Reconciliation of Federal Statutory Income Tax Rate to the Company's Effective Tax Rate (Detail)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory tax rate	(21.00%)	(21.00%)
State statutory tax rate, net of federal benefit	(7.00%)	(7.00%)
Research and development credits, net of uncertain tax positions	(2.60%)	(2.60%)
Derecognition due to Section 382 and 383	0.90%	25.40%
Stock-based compensation	0.70%	0.50%
Permanent items	(0.00%)	5.60%
Change in valuation allowance	29.00%	(0.90%)
Effective tax rate	(0.00%)	(0.00%)

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

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage 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 changes in the valuation allowance for deferred tax assets.

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to nondeductible expense for share-based payment arrangement.

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Percentage 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 applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Effective income tax rate reconciliation derecognition on operating loss carryforwards and research and development.

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Effective income tax rate reconciliation permanent items.

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