Income Taxes - Schedule of Reconciliation of Income Tax Expense Computed at Statutory Corporate Income Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Effective Income Tax Rate
Income tax expense at statutory rate	9.30%	9.30%	9.30%
State income tax, net of federal benefit	(2.10%)	0.70%	0.30%
Nondeductible expenses	(0.10%)	0.00%	0.00%
Foreign rate differential	2.00%	(0.40%)	(2.50%)
Statutory to US GAAP permanent differences	0.10%	1.00%	1.80%
Stock-based compensation	(2.00%)	1.40%	(2.90%)
Impact of deferred rate change	(12.20%)	0.00%	0.00%
Research credits	(5.20%)	1.80%	0.80%
Change in valuation allowance	10.90%	(14.10%)	(9.40%)
Effective income tax rate	0.70%	(0.30%)	(2.60%)

Effective income tax rate reconciliation nondeductible expense impact of deferred rate change.

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Effective income tax rate reconciliation statutory permanent differences.

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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 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 statutory income tax expense (benefit) outside of the country of domicile.

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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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