Note 2 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Fair Value		Level 1		Level 2		Level 3
Investments in debt securities (short-term)	$	4,415	$	705	$	3,710	$	-
Investments in debt securities (long-term)		7,074		908		6,166		-

Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]

	Balance Sheet
	Warrant Liability			APIC		Accum Def.
Balance as of 12/31/2018 (Prior to Adoption of ASU 2017-11)	$	925		$	279,306	$	(252,809	)
Reverse beginning balance as of January 1, 2018		(2,192	)		6,970		(4,778	)
Change in fair value of warrant liability		1,267			-		(1,267	)
Balance as of 12/31/2018 (After Adoption of ASU 2017-11)	$	-		$	286,276	$	(258,854	)

	Statement of Operations
	For the year ended December 31, 2018
	Change in Value of Warrant Liability			Net Loss and Comprehensive Loss
Balance as of 12/31/2018 (Prior to Adoption of ASU 2017-11)	$	1,267		$	(7,434	)
Reverse beginning balance as of January 1, 2018		-			-
Change in fair value of warrant liability		(1,267	)		(1,267	)
Balance as of 12/31/2018 (After Adoption of ASU 2017-11)	$	-		$	(8,701	)