Note 4 - Loans and the Allowance for Credit Losses - Collateral Dependent Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	$ 8,351,841	$ 8,109,161
Real Estate [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	59,576	71,925
Other Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	10,387	22,517
Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	69,963	94,442
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	1,578,730	1,472,734
Commercial Portfolio Segment [Member] | Real Estate [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	4,949	5,352
Commercial Portfolio Segment [Member] | Other Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	10,387	22,517
Commercial Portfolio Segment [Member] | Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	15,336	27,869
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	5,895,545	5,795,228
Commercial Real Estate Portfolio Segment [Member] | Real Estate [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	39,986	52,477
Commercial Real Estate Portfolio Segment [Member] | Other Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	0	0
Commercial Real Estate Portfolio Segment [Member] | Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	39,986	52,477
Commercial Construction Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	620,496	574,139
Commercial Construction Portfolio Segment [Member] | Real Estate [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	8,700	8,232
Commercial Construction Portfolio Segment [Member] | Other Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	0	0
Commercial Construction Portfolio Segment [Member] | Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	8,700	8,232
Residential Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	256,041	264,748
Residential Portfolio Segment [Member] | Real Estate [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	5,941	5,864
Residential Portfolio Segment [Member] | Other Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	0	0
Residential Portfolio Segment [Member] | Collateral Pledged [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	$ 5,941	$ 5,864