Note 15 - Share-Based and Other Compensation Programs Compensation Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement, Expense	[1]	$ 21,414	$ 17,649	$ 13,492
Share-based Compensation Arrangement, Amount Deferred as Policy Acquisition Cost		373	324	269
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost, Excluding Amounts Deferred as Policy Acquisition Costs, Prior to Income Taxes		21,041	17,325	13,223
Equity Compensation Plans
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 24,800
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		1 year 10 months 24 days
Employee Stock Purchase Plan
Share-based Payment Arrangement, Expense	[1]	$ 444	453	432
RSUs
Share-based Payment Arrangement, Expense	[1]	20,694	16,591	12,207
Non-Qualified Stock Options
Share-based Payment Arrangement, Expense	[1]	274	603	851
Phantom Stock
Share-based Payment Arrangement, Expense	[1]	$ 2	$ 2	$ 2

[1] Compensation cost is generally recognized over the periods that an employee provides service in exchange for the award. For purposes of calculating compensation cost recognized, we generally consider awards effectively vested (and we recognize the full compensation costs) when grantees become retirement eligible.