Note 7 - Deposits (Details Textual) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deposit Liabilities, Accrued Interest	$ 8.5	$ 22.3	$ 10.5
Geographic Distribution, Domestic [Member]
Time Deposits, at or Above FDIC Insurance Limit	2,900.0	3,100.0
Geographic Distribution, Foreign [Member]
Time Deposits, at or Above FDIC Insurance Limit	$ 142.8	$ 192.9