Note 12 - Commitments and Contingencies - Financial Instruments With Off-balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Commitments	$ 3,381,961	$ 2,973,155
Commitments to Extend Credit [Member]
Commitments	3,077,081	2,691,579
Standby Letters of Credit [Member]
Commitments	282,352	245,087
Commercial Letters of Credit [Member]
Commitments	22,209	35,759
Bill of Lading Guarantees [Member]
Commitments	$ 319	$ 730