Note 13 - Commitments and Off-balance-sheet Risk - Instruments Carried at Fair Values (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Contractual amounts of financial instruments with off-balance sheet risk	$ 1,430,195,000	$ 1,038,444,000
Standby Letters of Credit [Member]
Standby letters of credit, contract amount	20,543,000	22,798,000
Contractual amounts of financial instruments with off-balance sheet risk	$ 138,000	$ 160,000