Restructuring - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost And Reserve [Line Items]
Net restructuring charge	$ 995,000	$ (49,000)	$ 1,573,000	$ 2,129,000
Q3 2017 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses (benefits)	845,000		845,000
Net restructuring charge	800,000		800,000
Employee severance Costs	600,000		600,000
Other costs	200,000		200,000
Q2 2017 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses (benefits)			1,301,000
Net restructuring charge	1,300,000		1,300,000
Employee severance Costs	1,200,000		1,200,000
Other costs	100,000		100,000
Q2 2017 Restructuring Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses (benefits)	100,000
Q2 2015 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses (benefits)	$ (100,000)		$ (560,000)
Restructuring liability, expected paid out period			4 years 8 months 13 days