Note 12 - Commitments and Contingencies - Financial Instruments With Off-balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments	$ 3,228,787	$ 3,381,961
Commitments to Extend Credit [Member]
Commitments	2,977,528	3,077,081
Standby Letters of Credit [Member]
Commitments	234,200	282,352
Commercial Letters of Credit [Member]
Commitments	16,821	22,209
Bill of Lading Guarantees [Member]
Commitments	$ 238	$ 319