Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Percent, Total		17.80%	31.10%	27.10%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	35.00%	35.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 5,900	$ 5,900
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		846	$ 607	$ 866
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net, Total				$ 1,700
Deferred Tax Assets, Valuation Allowance, Total	326	154	326
Unrecognized Tax Benefits, Including Interest and Penalties	$ 29	29	29
Accounting Standards Update 2016-09 [Member]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		$ 549	$ 1,500