Note 6 - Note Payable (Details Textual) - USD ($)			3 Months Ended		9 Months Ended
	Dec. 29, 2017	May 22, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Interest Payable			$ 13,087,000		$ 13,087,000
Notes Payable, Noncurrent, Total			$ 31,694,000		$ 31,694,000		$ 30,528,000	[1]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			5,549		5,549
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		2,220	2,220		2,220
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 950	$ 950		$ 950
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			$ 331,000	$ 318,000	$ 973,000	$ 934,000
Debt Instrument, Prepayment Fee, Percentage		5.00%
Debt Instrument, Prepayment Fee, Period of Term		5 years
Debt Instrument, Covenant, Cash and Cash Equivalents		$ 2,000,000
Notes Payable, Noncurrent, Total			31,694,000		31,694,000		$ 30,528,000
The 2017 Loan Agreement [Member] | CRG LP [Member] | Other Noncurrent Liabilities [Member]
Interest Payable			$ 756,000		$ 756,000

[1] The condensed consolidated balance sheet as of December 31, 2018 has been derived from the audited consolidated financial statements as of that date.