Note 11 - Income Taxes (Details Textual) - USD ($) $ in Thousands		12 Months Ended
	Aug. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			34.00%
Deferred Tax Assets, Increase (Decrease) from Revaluation Due to Tax Rate Change			$ (2,200)
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			(54,100)	$ 8,800	$ 9,800
Operating Loss Carryforwards	$ 0
Tax Credit Carryforward, Amount	0		2,300	21,800	16,900
Unrecognized Tax Benefits			0	0	0
Deferred Tax Assets, Valuation Allowance			6,949	65,956	52,234
Deferred Tax Assets, Valuation Allowance, Increase (Decrease) from Revaluation Due to Tax Rate Change			(2,200)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			0	0	0
Deferred Tax Assets, Operating Loss Carryforwards			2,651	42,156	34,488
Accounting Standards Update 2016-09 [Member]
Deferred Tax Assets, Valuation Allowance						$ 600
Deferred Tax Assets, Operating Loss Carryforwards						$ 600
Current Year Deferred Tax Assets Activity [Member]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			13,100
Effect on Deferred Tax Assets of Section 382 Limitation [Member]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			(65,000)
Effect of Tax Rate Change on Deferred Tax Assets [Member]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			(2,200)
Series A Preferred Stock [Member]
Proceeds from Issuance of Convertible Preferred Stock	22,000
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%
Domestic Tax Authority [Member]
Income Tax Expense (Benefit)			0	0	0
Operating Loss Carryforwards			10,600	101,400	94,200
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Decrease in Net Operating Loss Carryforwards from Section 382 Limitation	107,300
Decrease in Net Operating Loss Carryforwards from Section 382 Limitation, Tax Affected	34,100
Decrease in Tax Credit Carryforward Amount from Section 382 Limitation	23,800
State and Local Jurisdiction [Member]
Income Tax Expense (Benefit)			0	0	0
Decrease in Net Operating Loss Carryforwards from Section 382 Limitation	5,000
Decrease in Tax Credit Carryforward Amount from Section 382 Limitation	$ 2,100
Operating Loss Carryforwards			$ 6,800	$ 53,000	$ 46,400