Acquisition of Senhance Surgical Robotic System - Summary of Fair Value Consideration (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Sep. 21, 2015	Nov. 30, 2016	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Contingent consideration			$ 12,418,000	$ 22,800,000
Senhance Surgical Robotic System Acquisition [Member]
Business Acquisition [Line Items]
Common shares issued	15,543,413
Closing price per share	$ 2.81
Consideration share value	$ 43,677,000
Cash consideration	25,000,000
Contingent consideration	23,900,000		$ 12,400,000
Total consideration	$ 92,577,000	$ 400,000