Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($)
Income Taxes [Line Items]
Income tax expense (benefit)	$ 0
Uncertain tax position	0
Deferred tax assets, valuation allowances	25,254,000
Unrecognized tax benefits	0
Tax interest and penalties	0
Domestic Tax Authority [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	59,357,000
Federal tax credits carryforwards	6,349,000
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	59,453,000
Federal tax credits carryforwards	$ 702,000