Note 5 - Loans and the Allowance for Credit Losses - Analysis of Aging of Loans (Details) - USD ($) $ in Thousands		Jun. 30, 2022	Dec. 31, 2021
Loans and Leases Receivable, Gross		$ 7,282,423	$ 6,838,351
Nonaccrual		60,756	61,700
Financial Asset, 30 to 59 Days Past Due [Member]
Loans and Leases Receivable, Gross		690	7,364
Financial Asset, 60 to 89 Days Past Due [Member]
Loans and Leases Receivable, Gross		3,252	2,030
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans and Leases Receivable, Gross		10,164	13,531
Financial Asset, Past Due [Member]
Loans and Leases Receivable, Gross		74,862	84,625
Financial Asset, Not Past Due [Member]
Loans and Leases Receivable, Gross		7,207,561	6,753,726
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Gross	[1]	1,354,625	1,299,428
Nonaccrual		29,138	30,062
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans and Leases Receivable, Gross		16	4,305
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans and Leases Receivable, Gross		358	729
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans and Leases Receivable, Gross		4,403	4,457
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans and Leases Receivable, Gross		33,915	39,553
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans and Leases Receivable, Gross		1,320,710	1,259,875
Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable, Gross		5,107,382	4,741,590
Nonaccrual		29,183	25,393
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	1,622
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans and Leases Receivable, Gross		2,894	1,009
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans and Leases Receivable, Gross		5,761	5,935
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans and Leases Receivable, Gross		37,838	33,959
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans and Leases Receivable, Gross		5,069,544	4,707,631
Commercial Construction Portfolio Segment [Member]
Loans and Leases Receivable, Gross		569,789	540,178
Nonaccrual		0	3,150
Commercial Construction Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Commercial Construction Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Commercial Construction Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Commercial Construction Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans and Leases Receivable, Gross		0	3,150
Commercial Construction Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans and Leases Receivable, Gross		569,789	537,028
Residential Portfolio Segment [Member]
Loans and Leases Receivable, Gross		249,379	255,269
Nonaccrual		2,435	3,095
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans and Leases Receivable, Gross		674	1,437
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	292
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	3,139
Residential Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans and Leases Receivable, Gross		3,109	7,963
Residential Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans and Leases Receivable, Gross		246,270	247,306
Consumer Portfolio Segment [Member]
Loans and Leases Receivable, Gross		1,248	1,886
Nonaccrual		0	0
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Consumer Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans and Leases Receivable, Gross		0	0
Consumer Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans and Leases Receivable, Gross		$ 1,248	$ 1,886

[1] Included in commercial loans as of June 30, 2022 and December 31, 2021 are PPP loans of $18.0 million and $93.1 million, respectively.