Property and Equipment - Depreciation and Amortization on Property and Equipment Using the Straight-Line Method (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Office furniture and fixtures	$ 1,194	$ 1,168
Software	2,661	2,146
Equipment	4,366	4,071
Leasehold improvements	1,620	1,617
Gross property and equipment	9,841	9,002
Less accumulated depreciation and amortization	(5,995)	(5,432)
Property and equipment, net	$ 3,846	$ 3,570