Note 5 - Loans and the Allowance for Credit Losses - Collateral Dependent Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Gross loans	$ 8,304,101	$ 8,351,841
Real Estate [Member]
Gross loans	35,742	59,576
Other Collateral Pledged [Member]
Gross loans	10,280	10,387
Collateral Pledged [Member]
Gross loans	46,022	69,963
Commercial Portfolio Segment [Member]
Gross loans	1,572,494	1,578,730
Commercial Portfolio Segment [Member] | Real Estate [Member]
Gross loans	1,700	4,949
Commercial Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	10,280	10,387
Commercial Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	11,980	15,336
Commercial Real Estate Portfolio Segment [Member]
Gross loans	5,829,950	5,895,545
Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member]
Gross loans	33,210	39,986
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	33,210	39,986
Commercial Construction Portfolio Segment [Member]
Gross loans	646,593	620,496
Commercial Construction Portfolio Segment [Member] | Real Estate [Member]
Gross loans	0	8,700
Commercial Construction Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	0	0
Commercial Construction Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	0	8,700
Residential Portfolio Segment [Member]
Gross loans	254,214	256,041
Residential Portfolio Segment [Member] | Real Estate [Member]
Gross loans	832	5,941
Residential Portfolio Segment [Member] | Other Collateral Pledged [Member]
Gross loans	0	0
Residential Portfolio Segment [Member] | Collateral Pledged [Member]
Gross loans	$ 832	$ 5,941