Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 5,900
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		$ 607	$ 866	$ 747
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net			1,700	$ 673
Deferred Tax Assets, Equity Method Investments	565	565	905
Deferred Tax Assets, Future Deductions for Compensation	19,000	19,000
Deferred Tax Liabilities, Fixed Assets	541	541
Deferred Tax Assets, Valuation Allowance	326	326	134
Unrecognized Tax Benefits, Including Interest and Penalties	$ 40	40	$ 40
Accounting Standards Update 2016-09 [Member]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		$ 1,500