Inventories - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Inventory [Line Items]
Write down of inventory			$ 2,565,000
SurgiBot System [Member]
Inventory [Line Items]
Write down of inventory	$ 0	$ 0	$ 2,600,000