Restructuring and Severance - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Feb. 14, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses		$ (2)	$ 258	$ (14)	$ 368
Restructuring accrual		$ 104		$ 104		$ 129	$ 129
3VR
Restructuring Cost And Reserve [Line Items]
Date of acquisition completed	Feb. 14, 2018			Feb. 14, 2018
Restructuring and severance expenses					400
Restructuring accrual							$ 100
3VR | Facility Rental
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses					200
3VR | Severance
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses					$ 200