Note 13 - Commitments and Contingencies (Details Textual) $ in Thousands, € in Millions	Dec. 30, 2016 EUR (€) shares	Sep. 21, 2015 shares	Sep. 30, 2020 USD ($)	Jul. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Combination, Contingent Consideration, Liability, Total			$ 2,780		$ 1,084
Restricted Cash Held with Silicon Valley Bank [Member]
Restricted Cash, Total				$ 500
Silicon Valley Bank [Member]
Letters of Credit Outstanding, Amount				$ 500
Office, Lab and Warehouse Space in Durham, North Carolina [Member]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract (Month)				125 months
Lessee, Operating Lease, Lease Not yet Commenced, Renewal Term (Year)				5 years
Lessee, Operating Lease, Liability, to be Paid, Total				$ 5,000
Senhance Surgical Robotic System Acquisition [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in shares) | shares	286,360	1,195,647
Business Combination, Contingent Consideration, Liability, Total			$ 2,800		$ 1,100
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable | €	€ 5