Note 4 - Loans and the Allowance for Credit Losses - Analysis of Aging of Loans (Details) - USD ($) $ in Thousands		Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		$ 8,109,161	$ 6,838,351
Nonaccrual		44,454	61,700
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		1,965	7,364
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	2,030
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		5,591	13,531
Financial Asset, Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		52,010	84,625
Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		8,057,151	6,753,726
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process	[1]	1,472,734	1,299,428
Nonaccrual		25,257	30,062
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		306	4,305
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	729
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	4,457
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		25,563	39,553
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		1,447,171	1,259,875
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		5,795,228	4,741,590
Nonaccrual		16,817	25,393
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		90	1,622
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	1,009
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		5,591	5,935
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		22,498	33,959
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		5,772,730	4,707,631
Commercial Construction Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		574,139	540,178
Nonaccrual		0	3,150
Commercial Construction Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Commercial Construction Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Commercial Construction Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Commercial Construction Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	3,150
Commercial Construction Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		574,139	537,028
Residential Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		264,748	255,269
Nonaccrual		2,380	3,095
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		1,569	1,437
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	292
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	3,139
Residential Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		3,949	7,963
Residential Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		260,799	247,306
Consumer Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		2,312	1,886
Nonaccrual		0	0
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Consumer Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		0	0
Consumer Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		$ 2,312	$ 1,886

[1] Included in commercial loans as of December 31, 2022 and December 31, 2021 were Paycheck Protection Program (“PPP”) loans of $11.4 million and $93.1 million, respectively. These loans are 100% federally guaranteed and currently not subject to any allocation of allowance for credit losses.