Note 6 - Loans and the Allowance for Credit Losses - Collateral Dependent Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Gross loans	$ 11,739,093	$ 11,457,558
Real Estate [Member]
Gross loans	236,862	254,710
Other Collateral Pledged [Member]
Gross loans	8,676	8,783
Collateral Pledged [Member]
Gross loans	245,538	263,493
Commercial Portfolio Segment [Member]
Gross loans	1,644,836	1,565,963
Commercial Portfolio Segment [Member] \| Real Estate [Member]
Gross loans	6,124	6,948
Commercial Portfolio Segment [Member] \| Other Collateral Pledged [Member]
Gross loans	8,676	8,783
Commercial Portfolio Segment [Member] \| Collateral Pledged [Member]
Gross loans	14,800	15,731
Commercial Real Estate Portfolio Segment [Member]
Gross loans	8,318,844	8,054,696
Commercial Real Estate Portfolio Segment [Member] \| Real Estate [Member]
Gross loans	225,669	242,125
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	225,669	242,125
Residential Portfolio Segment [Member]
Gross loans	1,202,539	1,210,980
Residential Portfolio Segment [Member] \| Real Estate [Member]
Gross loans	5,069	5,637
Residential Portfolio Segment [Member] \| Other Collateral Pledged [Member]
Gross loans	0	0
Residential Portfolio Segment [Member] \| Collateral Pledged [Member]
Gross loans	$ 5,069	$ 5,637