Equipment and Improvements - Summary of Equipment and Improvements (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Gross, Total	$ 20,961	$ 20,895
Less accumulated depreciation and amortization	(20,096)	(19,666)
Equipment and improvements, net	865	1,229
Computer Hardware, Software, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Gross, Total	14,683	14,617
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Gross, Total	5,316	5,316
Office Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Gross, Total	$ 962	$ 962