Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets, Valuation Allowance, Total	$ 41,281	$ 39,516
Unrecognized Tax Benefits, Ending Balance	2,482	2,482	$ 2,482	$ 2,482
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	200
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	1,100	$ 1,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	456,500
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,000
Domestic Tax Authority [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	14,300
Domestic Tax Authority [Member] | Alternative Minimum Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	5,500
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 1,077,500