Note 6 - Other Assets and Other Liabilities - Summary of Other Assets (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Federal Reserve Bank stock	[1]	$ 14,069	$ 14,069
Other investments		158	158
Total cost method equity investments		14,227	14,227
Life insurance cash surrender value		58,496	57,810
Net deferred tax asset		21,048	11,085
Right-of-use asset		17,246	17,136
Limited partnership investments		20,135	20,773
Interest receivable		28,998	28,797
Prepaid assets		4,237	3,737
Other assets		11,725	10,767
Total other assets		$ 176,112	$ 164,332

[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.