Note 8 - Deposits (Details Textual) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deposit Liabilities, Accrued Interest	$ 4.4	$ 2.9	$ 3.4
Geographic Distribution, Domestic [Member]
Time Deposits, at or Above FDIC Insurance Limit	1,900.0	1,800.0
Geographic Distribution, Foreign [Member]
Time Deposits, at or Above FDIC Insurance Limit	$ 152.0	$ 137.7