Income Taxes - Addtional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Operating Loss Carryforwards		$ 35,800
Deferred Tax Assets, Tax Credit Carryforwards, Research		1,542	$ 1,259
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount		$ (1,447)	3,001	$ 1,899
Research And Development Tax Credit Carryforward, Expiration Period		2028 years
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ 4,900
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		9,500	$ 11,000
Scenario, Plan [Member]
Income Tax [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Research and Development Expense [Member]
Income Tax [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Research		$ 1,500
Minimum [Member]
Income Tax [Line Items]
Operating Loss Carry forwards Expiration Period		2026