Income Taxes - Summary of Statutory Federal Tax Rate to Income or Loss before Taxes (Detail)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal tax benefit at statutory rate	21.00%	34.00%
Change in valuation allowance	99.00%	(7.00%)
Research and development credits		16.00%
Section 382 limitation	(109.00%)
Other non-deductible expenses	(11.00%)	(3.00%)
Change in rate differential		(38.00%)
Build-to-suit adjustments		(2.00%)
Total	0.00%	0.00%

Effective income tax rate reconciliation section three eighty two limitation.

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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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