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Fair Value - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Apr. 28, 2017
Sep. 30, 2017
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Fair Value Measurements Disclosure [Line Items]          
Transfers of assets between Level 1, Level 2, and Level 3 of the fair value hierarchy   $ 0 $ 0    
Transfers of liabilities between Level 1, Level 2, and Level 3 of the fair value hierarchy   $ 0 $ 0    
Warrants to purchase common shares 24,900,000        
Common stock, par value (in dollars per share) $ 0.001 $ 0.001 $ 0.001   $ 0.001
Offering price 1.00        
Fair value input, dividends   $ 0 $ 0    
Change in fair value of warrant liabilities   $ 22,887,000 $ 25,213,000    
Series A Warrant [Member]          
Fair Value Measurements Disclosure [Line Items]          
Warrants, exercise price $ 1.00        
Warrant expiration date Oct. 31, 2017        
Series A Warrant [Member] | Black-Scholes Merton Model [Member]          
Fair Value Measurements Disclosure [Line Items]          
Estimated fair value of warrants $ 2,500,000 $ 11,400,000 $ 11,400,000    
Fair value input, term 1 year   7 months    
Fair value input, risk free rate 1.07%   1.22%    
Fair value input, dividends $ 0   $ 0    
Fair value input, volatility 73.14%   87.70%    
Fair value input, share price $ 0.65 $ 1.43 $ 1.43    
Series B Warrant [Member]          
Fair Value Measurements Disclosure [Line Items]          
Warrants, exercise price $ 1.00 $ 1.00 $ 1.00    
Series B Warrant [Member] | Black-Scholes Merton Model [Member]          
Fair Value Measurements Disclosure [Line Items]          
Estimated fair value of warrants $ 6,200,000        
Fair value input, term 5 years        
Fair value input, risk free rate 1.81%        
Fair value input, dividends $ 0        
Fair value input, volatility 73.14%        
Fair value input, share price $ 0.65        
Series B Warrant [Member] | Monte Carlo Valuation Model [Member]          
Fair Value Measurements Disclosure [Line Items]          
Estimated fair value of warrants   $ 19,700,000 $ 19,700,000    
Fair value input, term     4 years 6 months 26 days    
Fair value input, risk free rate     1.86%    
Fair value input, dividends     $ 0    
Fair value input, volatility     87.70%    
Fair value input, share price   $ 1.43 $ 1.43    
Probability of additional financing in 2018 and 2019     100.00%    
Common Stock [Member]          
Fair Value Measurements Disclosure [Line Items]          
Number of common stock or warrants in each unit 1        
Common Stock [Member] | Series A Warrant [Member]          
Fair Value Measurements Disclosure [Line Items]          
Number of common stock or warrants in each unit 1        
Warrants, exercise price $ 1.00        
Common Stock [Member] | Series B Warrant [Member]          
Fair Value Measurements Disclosure [Line Items]          
Number of common stock or warrants in each unit 0.75        
Warrants, exercise price $ 1.00        
Senhance Surgical Robotic System Acquisition [Member]          
Fair Value Measurements Disclosure [Line Items]          
Fair value of contingent consideration     $ 1,226,000 $ 1,700,000