Restructuring - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	May 31, 2016	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost And Reserve [Line Items]
Inventory write-down related to restructuring			$ 2,565,000		$ 2,565,000
Restructuring and other charges		$ (21,000)	$ 3,085,000		3,064,000
Restructuring and other charges related to other non-cash charges					2,556,000
Disposal of long-lived assets				$ 0	1,000,000	$ 0
Patents [Member]
Restructuring Cost And Reserve [Line Items]
Write-off of intellectual property					1,562,000
SurgiBot System [Member]
Restructuring Cost And Reserve [Line Items]
Inventory write-down related to restructuring				0	2,600,000	0
SurgiBot System [Member] | Patents [Member]
Restructuring Cost And Reserve [Line Items]
Write-off of intellectual property				0	1,600,000	$ 0
Headcount, Discontinued Efforts and Cancellation of Contracts [Member] | SurgiBot System [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 5,700,000
Inventory write-down related to restructuring	2,600,000
Restructuring and other charges	3,100,000
Restructuring amount paid in cash	500,000
Employee severance costs	400,000
Restructuring and other charges related to cancellation of contracts	100,000
Restructuring and other charges related to other non-cash charges	2,600,000
Disposal of long-lived assets	1,000,000
Headcount, Discontinued Efforts and Cancellation of Contracts [Member] | SurgiBot System [Member] | Accrued Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total future payments under plan		$ 0		$ 0	$ 0
Headcount, Discontinued Efforts and Cancellation of Contracts [Member] | SurgiBot System [Member] | Patents [Member]
Restructuring Cost And Reserve [Line Items]
Write-off of intellectual property	$ 1,600,000