Note 2 - Accounting Policies (Details Textual) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			389
Income Tax Expense (Benefit)	$ 6,515	$ 5,113	$ 11,352	$ 9,853
Percentage of Revenue Out of Scope of ASU 2014-09			73.00%
Operating Leases, Future Minimum Payments Due	$ 20,800		$ 20,800
Accounting Standards Update 2016-09 [Member]
Excess Tax Deduction Exceeding Related Share-based Compensation, Operating Activities			1,600
Income Tax Expense (Benefit)			$ (666)