Note 2 - Summary of Significant Accounting Policies 1 (Details Textual)					3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Jul. 06, 2020 USD ($)	Apr. 27, 2020 USD ($)	Mar. 10, 2020 USD ($)	Dec. 11, 2019 shares	Sep. 30, 2020 USD ($) shares	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Sep. 30, 2019 USD ($)	Jun. 30, 2020	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 10, 2019 shares
Common Stock, Shares, Outstanding, Ending Balance (in shares) | shares				20,200,000	99,879,029		20,691,301			99,879,029		20,691,301	261,900,000
Retained Earnings (Accumulated Deficit), Ending Balance					$ (709,120,000)		$ (663,600,000)			$ (709,120,000)		$ (663,600,000)
Working Capital					26,100,000					26,100,000
Proceeds from Issuance of Equity Net										13,525,000	$ 0
Cash and Cash Equivalents, at Carrying Value, Ending Balance					19,964,000		9,598,000			19,964,000		9,598,000
Accounts Receivable, Credit Loss Expense (Reversal)					0			$ 1,600,000		0	1,630,000
Restricted Cash and Cash Equivalents, Noncurrent, Total					1,200,000		1,000,000.0			1,200,000		1,000,000.0
Accounts Receivable, Allowance for Credit Loss, Ending Balance					1,700,000		1,700,000			1,700,000		1,700,000
Impairment of Intangible Assets, Finite-lived					0			7,912,000		0	7,912,000
Finite-Lived Intangible Assets, Net, Ending Balance					24,139,000		28,596,000			24,139,000		28,596,000
Goodwill, Impairment Loss					0		79,000,000.0	78,969,000		0	78,969,000
Period Of Service Sale Arrangement (Year)									5 years
Period of Service Sale Arrangement at Stated Service Price (Year)									4 years
Operating Lease, Lease Income, Total					200,000			0		400,000	0
Revenue, Remaining Performance Obligation, Amount					3,000,000.0		3,700,000			3,000,000.0		3,700,000
Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total					100,000		200,000			100,000		200,000
Contract with Customer, Liability, Revenue Recognized					100,000			300,000		500,000	1,500,000
Inventory Write-down					0			800,000		0	761,000
Share-based Payment Arrangement, Expense					$ 1,900,000			3,400,000		$ 5,800,000	9,700,000
Common Stock, Capital Shares Reserved for Future Issuance (in shares) | shares					1,871,289					1,871,289
Number of Operating Segments										1
Assets, Total					$ 80,144,000		74,779,000			$ 80,144,000		74,779,000
Non-US [Member]
Assets, Total					56,500,000		60,500,000			56,500,000		60,500,000
System Sold in 2017 [Member]
Contract with Customer, Liability, Revenue Recognized											1,300,000
Safe Stitch Medical Inc [Member]
Goodwill, Ending Balance					93,800,000					93,800,000
Senhance Surgical Robotic System Acquisition [Member]
Goodwill, Ending Balance					38,300,000					38,300,000
Medical Surgery Technologies Limited [Member]
Goodwill, Ending Balance					9,600,000					$ 9,600,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options and RSUs, Grants in Period, Grant Date Value					4,000	$ 5,000
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options and RSUs, Grants in Period, Grant Date Value					9,000	$ 10,000
Patents [Member]
Finite-Lived Intangible Asset, Useful Life (Year)										10 years
Developed Technology Rights [Member]
Finite-Lived Intangible Assets, Net, Ending Balance					23,849,000		28,287,000			$ 23,849,000		28,287,000
Developed Technology Rights [Member] | Minimum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)										5 years
Developed Technology Rights [Member] | Maximum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)										7 years
Intellectual Property [Member]
Impairment of Intangible Assets, Finite-lived										$ 0	$ 0
Finite-Lived Intangible Assets, Net, Ending Balance					24,139,000		28,596,000			24,139,000		28,596,000
In Process Research and Development [Member]
Impairment of Intangible Assets, Finite-lived							0	$ 7,900,000
Finite-Lived Intangible Assets, Net, Ending Balance					$ 0		$ 2,470,000			$ 0		$ 2,470,000
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Seven Customers [Member]
Number of Major Customers										7
Concentration Risk, Percentage										69.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Eight Customers [Member]
Number of Major Customers												8
Concentration Risk, Percentage												85.00%
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Nine Customers [Member]
Number of Major Customers					9					9
Concentration Risk, Percentage					57.00%					58.00%
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Five Customers [Member]
Number of Major Customers								5			5
Concentration Risk, Percentage								83.00%			83.00%
Revenue Benchmark [Member] | Geographic Concentration Risk [Member] | UNITED STATES
Concentration Risk, Percentage					36.00%			7.00%		29.00%	5.00%
Revenue Benchmark [Member] | Geographic Concentration Risk [Member] | Europe [Member]
Concentration Risk, Percentage					46.00%			20.00%		50.00%	42.00%
Revenue Benchmark [Member] | Geographic Concentration Risk [Member] | Asia [Member]
Concentration Risk, Percentage					18.00%			73.00%		21.00%	53.00%
Assets, Total [Member] | Geographic Concentration Risk [Member] | UNITED STATES
Concentration Risk, Percentage										30.00%		19.00%
Assets, Total [Member] | Geographic Concentration Risk [Member] | Non-US [Member]
Concentration Risk, Percentage										70.00%		81.00%
Paycheck Protection Program CARES Act [Member]
Proceeds from Issuance of Long-term Debt, Total		$ 2,815,200
Public Offering [Member]
Proceeds from Issuance of Equity Net	$ 13,600,000		$ 13,500,000
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio				13