Restructuring Charges - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 756,000	$ 756,000
Additional restructuring charges		0
One-time Severance and Other Employee-related Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges		400,000
Future Obligations Due under Manufacturing and Development Contracts [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges		300,000
Stock-based Compensation Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges		17,000
Fixed Asset Impairments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	14,000	14,000
Severance and Employee-related Costs and Future Contractual Obligations [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve	700,000	700,000
Restructuring payments expected to be paid in remainder of 2017	300,000	300,000
Restructuring payments expected to be paid in 2018 or beyond	400,000	$ 400,000
Severance [Member]
Restructuring Cost And Reserve [Line Items]
Payments for restructuring	$ 23,000