Note 5 - Loans and the Allowance for Credit Losses (Details Textual) Pure in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022 USD ($)	Sep. 30, 2021	Sep. 30, 2022 USD ($)	Sep. 30, 2021	Dec. 31, 2021 USD ($)
Loans and Leases Receivable, Gross		$ 7,910,013,000		$ 7,910,013,000		$ 6,838,351,000
Loans and Leases Receivable, Net of Deferred Income		7,900,450,000		7,900,450,000		6,828,622,000
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend		0		0
Financing Receivable, Troubled Debt Restructuring		$ 74,500,000		$ 74,500,000		79,500,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts		0	0	0	0
Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Loss, Ending Balance		$ 7,500,000		$ 7,500,000		10,400,000
Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring		27,500,000		27,500,000		35,900,000
Performing Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring		47,000,000.0		47,000,000.0		43,600,000
Asset Pledged as Collateral [Member] | Federal Home Loan Bank Advances [Member]
Loans and Leases Receivable, Net of Deferred Income		2,600,000,000		2,600,000,000		2,500,000,000
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Gross	[1]	1,448,727,000		1,448,727,000		1,299,428,000
Commercial Portfolio Segment [Member] | Paycheck Protection Program CARES Act [Member]
Loans and Leases Receivable, Gross		11,500,000		11,500,000		93,100,000
Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable, Gross		$ 5,666,848,000		5,666,848,000		$ 4,741,590,000
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring, One Time Principal Payment				$ 500,000

[1] Includes PPP loans of $11.5 million and $93.1 million as of September 30, 2022 and December 31, 2021 , respectively.