Note 1 - General (Details Textual) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020	[1]	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019	[1]	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020	Apr. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents, at Carrying Value, Ending Balance	$ 15,601						$ 25,028						$ 15,601	$ 25,028
Lessee, Operating Lease, Discount Rate	12.00%												12.00%
Operating Lease, Cost													$ 500	500
Operating Lease, Payments													600	600
Lessor, Operating Lease, Term of Contract (Month)																18 months
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance	$ 62,875						101,741						62,875	101,741			$ 66,979
Operating Income (Loss), Total	(1,631)	[1]	$ (2,275)		$ (2,028)	$ (3,532)	(2,060)	[1]	$ (2,262)		$ (2,603)	$ (3,057)	(9,466)	(9,982)
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance	(736,639)						$ (697,223)						(736,639)	$ (697,223)			$ (731,105)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2014-09 [Member]
Operating Income (Loss), Total													1,800
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance															$ 1,800
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2014-09 [Member] | Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance															$ (1,800)
Revolving Credit Facility [Member]
Debt Instrument, Debt Covenants, Cash and Cash Equivalent Threshold	$ 50,000												$ 50,000

[1] The three months ended December 31, 2019 includes equity income of $1.4 million related to an equity method investment that should have been recorded during the three months ended September 30, 2019. There was no impact on the full year results.