Income Taxes - Addtional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Line Items]
Operating Loss Carryforwards	$ 43,800
Deferred Tax Assets, Tax Credit Carryforwards, Research	1,780	$ 1,542
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ 1,845	$ (1,447)	$ 3,001
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	$ 11,400	$ 9,500
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	35,800
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	$ 8,000
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	$ 1,800
Minimum [Member]
Income Tax [Line Items]
Operating Loss Carry forwards Expiration Period	2026