Note 14 - Commitments and Off-balance-sheet Risk - Instruments Carried at Fair Values (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Standby letters of credit, carrying value	$ 1,038,444,000	$ 1,036,775,000
Standby Letters of Credit [Member]
Standby letters of credit, contract amount	22,798,000	25,322,000
Standby letters of credit, carrying value	$ 160,000	$ 126,000