Note 5 - Loans and the Allowance for Credit Losses - Collateral Dependent Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Gross loans	$ 8,141,176	$ 8,109,161
Real Estate [Member]
Gross loans	68,959	71,925
Other Collateral Pledged [Member]
Gross loans	16,650	22,517
Collateral Pledged [Member]
Gross loans	85,609	94,442
Commercial Portfolio Segment [Member]
Gross loans	1,414,226	1,472,734
Commercial Portfolio Segment [Member] | Real Estate [Member]
Gross loans	4,950	5,352
Commercial Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	16,650	22,517
Commercial Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	21,600	27,869
Commercial Real Estate Portfolio Segment [Member]
Gross loans	5,835,880	5,795,228
Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member]
Gross loans	49,529	52,477
Commercial Real Estate Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	49,529	52,477
Commercial Construction Portfolio Segment [Member]
Gross loans	630,469	574,139
Commercial Construction Portfolio Segment [Member] | Real Estate [Member]
Gross loans	8,366	8,232
Commercial Construction Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	0	0
Commercial Construction Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	8,366	8,232
Residential Portfolio Segment [Member]
Gross loans	259,166	264,748
Residential Portfolio Segment [Member] | Real Estate [Member]
Gross loans	6,114	5,864
Residential Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	0	0
Residential Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	$ 6,114	$ 5,864