Restructuring Charges - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 777,000
Additional restructuring charges	0
Restructuring	249,000
Restructuring payments expected to be paid in 2018 or beyond	100,000
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
Prepaid Amortization Associated With Manufacturing Contracts [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 37,500