Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Apr. 14, 2020	Feb. 20, 2020	Dec. 31, 2019	Oct. 01, 2019	Dec. 31, 2018
Revenue from Contract with Customer, Including Assessed Tax	$ 6,248	$ 4,281
Retained Earnings (Accumulated Deficit), Ending Balance	(694,561)				$ (677,760)
Cash and Cash Equivalents, at Carrying Value, Ending Balance	29,531	109,587			42,049		$ 137,686
Cash and Cash Equivalents, Period Increase (Decrease), Total	(12,500)
Accounts Receivable, after Allowance for Credit Loss, Current, Total	6,190				15,976
Restricted Cash and Cash Equivalents, Noncurrent, Total	2,653	1,540			3,016		$ 1,534
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance	4,259				$ 3,794
Bridge Loan [Member]
Debt Agreement, Maximum Borrowing Capacity	$ 10,000
Debt Instrument, Interest Rate, Stated Percentage	9.50%
Product [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,359
Pending Merger with Lantheus Holdings, Inc [Member]
Conversion of Stock, Shares Converted per Common Stock Issued and Outstanding (in shares)				0.31		0.2502
Business Combination, Maximum Consideration Paid, Percentage of Total Consideration Received				19.90%
Ownership Percentage After Merger				40.00%		35.00%
Pending Merger with Lantheus Holdings, Inc [Member] | Velan Stockholders [Member] | Subsequent Event [Member]
Liabilities from Reimbursement for Expenses with Stockholders Involvement			$ 1,300