Note 2 - Restatement of Consolidated Financial Statements (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018	Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Jan. 01, 2018	Dec. 31, 2017
Stockholders' Equity Attributable to Parent, Ending Balance	$ (100,052)	$ (103,035)		$ (113,304)		$ (117,556)		$ (98,395)	$ (119,268)	[1]	$ (94,722)		$ (68,284)		$ (73,051)
Stockholders' Equity Attributable to Parent, Ending Balance	$ 43,454	35,191		2,072		(3,740)		14,632	(6,495)		(12,944)		(4,253)		(9,532)	$ (9,532)
Revision of Prior Period, Adjustment [Member]
Stockholders' Equity Attributable to Parent, Ending Balance		(42,585)	[1],[2]	(43,538)	[1],[2]	(46,952)	[1]	(27,364)	(47,404)	[1]	(21,707)	[1]	5,776	[1]	907
Stockholders' Equity Attributable to Parent, Ending Balance		$ (41,771)		$ (44,194)		$ (48,106)		$ (28,516)	$ (50,425)		$ (32,599)		$ (14,725)		$ (19,624)

[1] Adjustments related to recording certain warrants as liabilities, see Note 2: "Restatement of Consolidated Financial Statements".

[2] Adjustments related to change in valuation method of market-based restricted stock awards.