Restructuring - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Net restructuring charge	$ 1,400	$ 600
Q2 2017 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charge	1,300	1,300
Employee severance Costs	1,200	1,200
Other costs	100	100
Restructuring liability	125	125	$ 0
Restructuring benefits		(1,273)
Q2 2015 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring liability	15,940	15,940	$ 19,388
Additional expenses	100
Restructuring benefits		$ 676
Restructuring liability, expected paid out period		4 years 10 months 24 days
Research and Development [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charge	1,300	$ 300
General and Administrative [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charge	$ 100	$ 300