Note 5 - Mortgage Servicing Rights (Details Textual) - Mortgage Servicing Rights [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Disclosure, off-Balance-Sheet Risks, Face Amount, Asset	$ 2,832,016	$ 2,783,458
Servicing Asset at Fair Value, Amount	38,200	35,500
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	$ 7,200	$ 7,100	$ 6,300
Minimum [Member]
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of Other than 10 or 20 Percent Adverse Change in Other Assumption, Percent	0.50%
Maximum [Member]
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of Other than 10 or 20 Percent Adverse Change in Other Assumption, Percent	1.00%