Note 6 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			$ (56,500,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
Deferred Income Tax Expense (Benefit), Excluding Effective Changes in Tax Rate			$ 8,000,000.0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Excluding Changes in Tax Rate, Percent			40.10%
Unrecognized Tax Benefits, Ending Balance	$ 3,000,000.0	$ 1,900,000
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	1,100,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,900,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	$ 13,000	$ 12,000
Domestic Tax Authority [Member]
Open Tax Year	2016 2017 2018 2019