Restructuring - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Position	Jun. 30, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring plan implemented date			Jun. 06, 2018
Number of Eliminated positions | Position			48
Restructuring charges	$ 6,376		$ 6,570
Revised stock based compensation expense	3,188	$ 5,192	7,435	$ 10,023
Future cash expenditures	2,400		2,400
Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Revised stock based compensation expense	$ 1,402		$ 1,402