Note 13 - Employee Benefit Plans (Details Textual) - USD ($)		12 Months Ended
	Dec. 31, 1998	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan, Employer Discretionary Contribution Amount		$ 639,000	$ 574,000	$ 520,000
Stock Purchased by Employee Stock Ownership Plan, Shares (in shares)	61,501
Employee Stock Ownership Plan (ESOP) Loan Payments From ESOP Loan Term (Year)	10 years
Employee Stock Ownership Plan (ESOP), Compensation Expense		$ 0	$ 0	$ 0
Employee Stock Ownership Plan (ESOP), Number of Allocated Shares (in shares)		52,004	52,200