Note 1 - Summary of Significant Accounting Policies - Noninterest Income (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Service Charges on Deposit and Sweep Accounts [Member]
Noninterest revenue	$ 5,078,000	$ 4,578,000	$ 4,584,000
Credit and Debit Card [Member]
Noninterest revenue	7,516,000	5,973,000	5,925,000
Payroll Processing [Member]
Noninterest revenue	1,815,000	1,745,000	1,626,000
Customer Service [Member]
Noninterest revenue	$ 878,000	$ 785,000	$ 759,000