Property and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 500,000	$ 400,000	$ 1,400,000	$ 1,100,000
Disposal of property and equipment	0		200,000
Equipment purchased under equipment loans			1,500,000
Restructuring charges	756,000		756,000
Fixed Asset Impairments [Member]
Property, Plant and Equipment [Line Items]
Restructuring charges	$ 14,000		$ 14,000