Note 13 - Commitments and Contingencies - Financial Instruments With Off-balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Commitments	$ 2,973,155	$ 2,534,559
Commitments to Extend Credit [Member]
Commitments	2,691,579	2,366,368
Standby Letters of Credit [Member]
Commitments	245,087	140,814
Commercial Letters of Credit [Member]
Commitments	35,759	27,353
Bill of Lading Guarantees [Member]
Commitments	$ 730	$ 24