Note 3 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)		3 Months Ended			9 Months Ended
		Sep. 30, 2021		Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020	Dec. 31, 2020
Loans and Leases Receivable, Net of Deferred Income, Total		$ 3,313,709,000			$ 3,313,709,000			$ 3,193,470,000
Loans and Leases Receivable Period Increase (Decrease)					$ 120,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)					3.80%
Impaired Financing Receivable, Interest Income, Accrual Method, Total		400,000		$ 200,000	$ 1,200,000		$ 800,000
Loans and Leases Receivable, Nonaccrual Loans, Interest Income Recognized		0		0	0		0
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans		100,000		$ 100,000	$ 100,000		$ 200,000
Minimum Number of Days Past Due at Period End For Loans Modified as Troubled Debt Restructurings (Day)					30 days
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income, Total		2,842,359,000			$ 2,842,359,000			2,793,962,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Loans and Leases Receivable, Net of Deferred Income, Total	[1]	1,074,394,000			1,074,394,000			1,145,423,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Grades 1-4 [Member]
Loans and Leases Receivable, Net of Deferred Income, Total		706,369,000	[2]		706,369,000	[2]		828,706,000	[3]
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member]
Loans and Leases Receivable, Net of Deferred Income, Total		116,000,000			116,000,000			365,000,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member] | Grades 1-4 [Member]
Loans and Leases Receivable, Net of Deferred Income, Total		$ 116,000,000			$ 116,000,000			$ 365,000,000

[1] Includes $116 million and $365 million in loans originated under the Paycheck Protection Program for September 30, 2021 and December 31, 2020, respectively.

[2] Included in Commercial and Industrial Loans Grades 1 – 4 are $116 million of loans originated under the Paycheck Protection Program.

[3] Included in Commercial and Industrial Loans Grades 1 – 4 are $365 million of loans originated under the Paycheck Protection Program.