Acquisition of ALF-X Surgical Robotic System - Summary of Business Acquisition, ProForma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Net loss per share	$ 0.13	$ 0.19	$ 0.43	$ 0.53
ALF-X Surgical Robotic System Acquisition [Member]
Business Acquisition [Line Items]
Revenue	$ 77	$ 61	$ 77	$ 267
Net loss	$ 12,597	$ 14,575	$ 38,058	$ 38,869