Note 14 - Commitments and Off-balance-sheet Risk - Instruments Carried at Fair Values (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Standby letters of credit, carrying value	$ 1,036,775,000	$ 1,012,197,000
Standby Letters of Credit [Member]
Standby letters of credit, contract amount	25,322,000	26,030,000
Standby letters of credit, carrying value	$ 126,000	$ 122,000