Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Right-of-use assets (1)	$ 8,903	$ 8,600
Current lease liabilities	517	300	$ 0
Noncurrent lease liabilities (4)	$ 14,117	13,700
Lease Incentives And Deferred Rent Reduction Of ROU Asset Beginning Balance		$ 5,400