Note 7 - Note Payable (Details Textual)					12 Months Ended
	Nov. 26, 2019 USD ($) $ / shares	Nov. 12, 2019 USD ($) $ / shares shares	Dec. 29, 2017 USD ($)	May 22, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares					24,737,618	6,408
Debt Conversion, Converted Instrument, Amount					$ 35,529,000
Notes Payable, Noncurrent, Total					3,983,000	30,528,000
Share Price | $ / shares	$ 0.869
Gains (Losses) on Restructuring of Debt	$ (6,705,000)				$ (6,705,000)
Series B Preferred Stock [Member]
Conversion of Stock, Conversion Rate | $ / shares					$ 1.53
Preferred Stock, Fair Value, Per Share | $ / shares	$ 1,023.23
Convertible Preferred Stock, Fair Value	$ 32,027,000
Series B Preferred Stock [Member] | Measurement Input, Option Volatility [Member]
Convertible Preferred Stock, Measurement Input	73
Series B Preferred Stock [Member] | Measurement Input, Expected Term [Member]
Convertible Preferred Stock, Measurement Input	2
Series B Preferred Stock [Member] | Measurement Input, Risk Free Interest Rate [Member]
Convertible Preferred Stock, Measurement Input	1.58
Minimum [Member] | Series B Convertible Preferred Stock Into Common Stock [Member]
Conversion of Stock, Conversion Rate | $ / shares		$ 1.53
Maximum [Member] | Series B Convertible Preferred Stock Into Common Stock [Member]
Conversion of Stock, Conversion Rate | $ / shares		$ 1.836
Conversion of Term Loan with CRG Into Stock and Warrants [Member]
Debt Conversion, Original Debt, Amount		$ 28,981,000
Debt Conversion, Converted Instrument, Amount		$ 31,300,000
Conversion of Term Loan with CRG Into Series B Convertible Preferred Stock [Member]
Debt Conversion, Converted Instrument, Shares Issued | shares		31,300
May 2017 Issuance Related to 2017 Loan Agreement [Member]
Warrants and Rights Outstanding, Term				10 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares				2,220	2,220	2,220
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares				$ 950	$ 950	$ 950
Warrants and Rights Outstanding				$ 940,000
Warrants Issued Upon Conversion of Term Loan with CRG [Member]
Warrants and Rights Outstanding, Term		5 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares		9,893,776			9,893,776
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares					$ 1.84
Class of Warrants and Rights Outstanding, Exercise Price Percentage of Conversion Rate		120.00%
Warrants and Rights Outstanding	$ 3,502,000	$ 3,502,000
The 2017 Loan Agreement [Member] | CRG LP [Member]
Debt Instrument, Face Amount				20,000,000
Debt Agreement, Covenant, Additional Funding				10,000,000
Debt Agreement, Maximum Borrowing Capacity				$ 30,000,000
Proceeds from Lines of Credit, Total			$ 10,000,000
Debt Instrument, Term				6 years
Debt instrument, Interest Only Payment, Period				4 years
Debt Instrument, Interest Rate, Stated Percentage				12.50%
Debt Instrument, Interest Rate, Stated Percentage Deferred During Interest-only Period				4.00%
Paid-in-Kind Interest					$ 1,226,000	$ 1,256,000
Debt Instrument, Prepayment Fee, Percentage				5.00%
Debt Instrument, Covenant, Cash and Cash Equivalents				$ 2,000,000
Debt Instrument, Back-end Facility Fee Percentage of Principal		25.00%		5.00%
Notes Payable, Noncurrent, Total					$ 3,983,000	$ 30,528,000