Note 14 - Benefit Plans (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2014
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	5.00%			4.25%
Defined Contribution Plan, Cost	$ 1.9	$ 1.7	$ 1.6
Interest Expense, Deferred Compensation Plan	$ 0.1	$ 0.1	$ 0.1
Common Stock Including Additional Paid in Capital [Member]
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)	2,264	1,507	1,579
Stock Purchase Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	250,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)	239,000
Other Liabilities [Member]
Deferred Compensation Liability, Current and Noncurrent, Total	$ 2.4	$ 2.7