Note 13 - Commitments and Contingencies - Financial Instruments With Off-balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitments	$ 2,534,559	$ 2,174,995
Commitments to Extend Credit [Member]
Commitments	2,366,368	2,062,241
Standby Letters of Credit [Member]
Commitments	140,814	75,396
Commercial Letters of Credit [Member]
Commitments	27,353	37,283
Bill of Lading Guarantees [Member]
Commitments	$ 24	$ 75