Note 6 - Other Assets and Other Liabilities - Summary of Other Assets (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
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		56,725	56,083
Net deferred tax asset		27,332	42,256
Right-of-use asset		17,891
Limited partnership investments		9,343	10,219
Interest receivable		23,947	25,834
Prepaid assets		4,373	4,658
Other assets		11,498	9,629
Total other assets		$ 165,336	$ 162,906

[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.