Note 1 - Basis of Presentation (Details Textual) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended				6 Months Ended
	Mar. 05, 2020	Mar. 31, 2020	May 31, 2017	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jul. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Nov. 30, 2018
Net Income (Loss) Attributable to Parent, Total				$ (4,793)	$ (20,514)	$ (7,476)	$ (7,260)	$ (25,307)	$ (14,736)
Gain (Loss) on Extinguishment of Debt, Total								(12,394)	0
Working Capital				2,100				2,100
Net Cash Provided by (Used in) Operating Activities, Total								(7,019)	(6,872)
Proceeds from Issuance of Common Stock								3,923	$ 14,642
Debt Instrument, Face Amount				$ 27,300				27,300
Debt Conversion, Original Debt, Amount								38,900
Required Payment to Acquire Property Available for Purchase, Due End of Fiscal Year	$ 19,000
Percentage of Future Quarterly Interest Payments												25.00%
Interest Paid, Excluding Capitalized Interest, Operating Activities								$ 715
Stock Issued During Period, Shares, Conversion of Convertible Securities (in shares)								5,766,337
Preferred Stock, Shares Issued, Total (in shares)				10,000				10,000			0
Senior Secured Debt [Member]
Debt Instrument, Face Amount			$ 60,000
Debt Instrument, Additional Amount after Refinance			15,000
Prior Senior Secured Debt [Member]
Extinguishment of Debt, Amount			$ 45,000
2020 Convertible Senior Notes [Member]
Debt Instrument, Face Amount	$ 27,400
Debt Instrument, Interest Rate, Stated Percentage	7.00%
Debt Conversion, Original Debt, Amount	$ 27,300
Debt Conversion, Converted Instrument, Shares Issued (in shares)	10,000
Conversion of Convertible Senior Notes 2020 into Common Stock [Member]
Debt Conversion, Original Debt, Amount	$ 17,500
Debt Conversion, Converted Instrument, Amount	2,600
July 2020 ATM Offering [Member] | Subsequent Event [Member]
At Market Issuance Sales Agreement, Maximum Aggregate Offering Price										$ 30,000
At Market Issuance Sales Agreement [Member]
At Market Issuance Sales Agreement, Maximum Aggregate Offering Price													$ 25,000
Stock Issued During Period, Shares, New Issues (in shares)		2,369,170
Proceeds from Issuance of Common Stock, Gross		$ 25,000
Proceeds from Issuance of Common Stock		$ 24,200
Conversion of Convertible Senior Notes 2020 into Preferred Stock [Member]
Gain (Loss) on Extinguishment of Debt, Total					$ (12,400)
Debt Conversion, Original Debt, Amount	$ 27,300
Debt Conversion, Converted Instrument, Shares Issued (in shares)	10,000