Note 10 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	35.00%	35.00%
Net Deferred Tax Asset Before Valuation Allowance	$ 12,715	$ 12,715	$ 12,334	$ 12,715
Effective Income Tax Rate Reconciliation, Percent, Total			15.00%	27.00%
Deferred Tax Assets, Operating Loss Carryforwards, Total	5,549	5,549	$ 3,541	$ 5,549
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		8,800
Deferred Tax Assets, Unrealized Losses on Available-for-Sale Securities, Gross	2,789	2,789	3,935	2,789
Deferred Tax Assets, Valuation Allowance, Total	0	$ 0		0	$ 12,200
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax Asset Valuation Allowance	$ 10,600
Liability for Uncertainty in Income Taxes, Current			0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total			$ 0	$ 0	$ 0