Note 8 - Commitments and Off-balance Sheet Risk - Exposure to Credit Losses (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Contractual amounts of financial instruments with off-balance sheet risk	$ 1,427,008,000	$ 1,430,195,000
Standby Letters of Credit [Member]
Contractual amounts of financial instruments with off-balance sheet risk	25,933,000	20,543,000
Unused lines of Credit [Member] | Commercial Portfolio Segment [Member]
Contractual amounts of financial instruments with off-balance sheet risk	1,052,778,000	1,019,496,000
Unused lines of Credit [Member] | One to Four Family Mortgages [Member]
Contractual amounts of financial instruments with off-balance sheet risk	59,986,000	59,396,000
Unused lines of Credit [Member] | Consumer Credit Card [Member]
Contractual amounts of financial instruments with off-balance sheet risk	76,556,000	72,495,000
Unused lines of Credit [Member] | Consumer Other Financing Receivable 1 [Member]
Contractual amounts of financial instruments with off-balance sheet risk	35,207,000	30,707,000
Loan Origination Commitments [Member]
Contractual amounts of financial instruments with off-balance sheet risk	$ 176,548,000	$ 227,558,000