Note 6 - Other Assets and Other Liabilities - Other Assets (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Dec. 31, 2022
Cost method equity investments:
Federal Reserve Bank stock (1)	[1]	$ 14,069	$ 11,743
Other investments		158	158
Total cost method equity investments		14,227	11,901
Life insurance cash surrender value		65,606	63,816
Net deferred tax asset		136,458	125,140
Right-of-use asset		18,593	15,746
Limited partnership investments		30,107	34,421
Interest receivable		55,597	53,558
Prepaid assets		4,447	4,894
Other assets		8,941	9,670
Total other assets		$ 333,976	$ 319,146

[1] A bank applying for membership in the Federal Reserve System is required to subscribe to stock in the Federal Reserve Bank (FRB) in its district in a sum equal to six percent of the bank’s paid-up capital stock and surplus. One-half of the amount of the bank's subscription shall be paid to the FRB and the remaining half will be subject to call when deemed necessary by the Board of Governors of the Federal Reserve System.