Property and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation expense related to plant and equipment	$ 590,000	$ 618,000	$ 626,000
Amount disposed of property plant and equipment	1,000,000	238,000	378,000
Gain or loss on disposal of property plant and equipment	$ 13,000	$ 10,000	$ 0