Fair Value - Quantitative Information about Inputs and Valuation Methodologies Used for Fair Value Measurements Classification (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares
Measurement Input, Discount Rate | Senhance Surgical Robotic System Acquisition | Level 3 | Contingent Consideration | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.10	0.115
Measurement Input, Discount Rate | Senhance Surgical Robotic System Acquisition | Level 3 | Contingent Consideration | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.11	0.12
Series B Warrant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value | $	$ 2.4	$ 4.6
Share price (in dollars per share) | $ / shares	$ 1.47	$ 29.38
Probability of additional financing in 2020	100.00%
Probability of additional financing in 2019		100.00%
Series B Warrant | Measurement Input, Expected Term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term	2 years 3 months 25 days	3 years 3 months 25 days
Series B Warrant | Measurement Input, Risk Free Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	0.0159	0.0247
Series B Warrant | Measurement Input, Expected Dividend Payment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	0	0
Series B Warrant | Measurement Input, Price Volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input	1.0980	0.8760