Restructuring and Severance - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Feb. 14, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses		$ (87,000)	$ 223,000	$ (101,000)	$ 591,000
Restructuring accrual						$ 104,000	$ 129,000
Restructuring accrual reversed		$ 91,000,000
3VR
Restructuring Cost And Reserve [Line Items]
Date of acquisition completed	Feb. 14, 2018			Feb. 14, 2018
Restructuring and severance expenses			223,000		591,000
Restructuring accrual							$ 129,000
3VR | Facility Rental
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses			102,000		280,000
3VR | Severance
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses			$ 121,000		$ 311,000