v3.19.2

Note 6 - Long-term Debt (Details Textual) - USD ($)		3 Months Ended		6 Months Ended
	May 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 02, 2017
Repayments of Long-term Debt, Total				$ 3,470,000	$ 3,762,000
Interest Expense, Total		$ 500,000	$ 586,000	876,000	1,229,000
Amortization of Debt Discount (Premium)				234,000	344,000
Warrant In Connection with Oxford Finance Loan Agreement [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	176,679
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 2.83
Loan Agreement with Oxford Finance LLC [Member]
Debt Instrument, Final Payment, Percentage of Aggregate Principal Amount	5.00%
Debt Instrument, Face Amount	$ 25,000,000
Repayments of Long-term Debt, Total	8,900,000
Interest Expense, Total		300,000
Amortization of Debt Discount (Premium)				100,000
Proceeds from Debt, Net of Issuance Costs and Repayment of Debt	$ 15,900,000
Debt Instrument, Interest Rate, Base Percentage	2.50%
Prepayment Charge, Percentage of Outstanding Balance, Before May 30,2020	2.00%
Prepayment Charge, Percentage of Outstanding Balance, After May 30, 2020, Before May 30, 2021	1.50%
Prepayment Charge, Percentage of Outstanding Balance, After May 30,2021	1.00%
Debt Instrument, Covenant, Minimum Required Unrestircted Cash	$ 5,000,000
Debt Instrument, Minimum Indebtedness Amount with Acceleration Right	250,000
Loan Default Events, Trigger of Negative Impact of Government Approvals and Judgments	$ 500,000
Debt Instrument, Default Additional Interest Rate	5.00%
Fair Value of Contingent Put Option, Liability	$ 700,000	700,000		700,000
Loan Agreement with Oxford Finance LLC [Member] | Minimum [Member]
Net Unrestricted Cash Proceeds, Contingent Threshold for Interest Only Period of Loan	$ 45,000,000
Loan Agreement with Oxford Finance LLC [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	6.75%
Hercules Loan and Security Agreement [Member]
Debt Instrument, Final Payment, Percentage of Aggregate Principal Amount						6.50%
Debt Instrument, Face Amount						$ 20,500,000
Repayments of Long-term Debt, Total	$ 8,900,000
Long-term Debt, Gross	7,400,000
Debt Instrument, Termination Fee	1,300,000
Gain (Loss) on Extinguishment of Debt, Total	$ (200,000)
Interest Expense, Total		200,000	600,000	600,000	1,200,000
Amortization of Debt Discount (Premium)		$ 100,000	$ 100,000	$ 200,000	$ 300,000

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