Note 7 - Deposits (Details Textual) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deposit Liabilities, Accrued Interest	$ 22.3	$ 10.5	$ 4.4
Geographic Distribution, Domestic [Member]
Time Deposits, at or Above FDIC Insurance Limit	3,100.0	2,800.0
Geographic Distribution, Foreign [Member]
Time Deposits, at or Above FDIC Insurance Limit	$ 192.9	$ 174.4