Note 3 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable, Net of Deferred Income, Total		$ 3,216,358,000		$ 2,856,667,000	$ 2,753,085,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total		1,300,000		1,300,000	1,100,000
Loans and Leases Receivable, Nonaccrual Loans, Interest Income Recognized		100,000		100,000	100,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans		$ 200,000		100,000	300,000
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		$ 2,793,962,000		2,441,544,000	$ 2,360,106,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Loans and Leases Receivable, Net of Deferred Income, Total	[1]	1,145,423,000		846,551,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Grades 1-4 [Member]
Loans and Leases Receivable, Net of Deferred Income, Total		828,706,000	[2]	$ 521,920,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member]
Loans and Leases Receivable, Net of Deferred Income, Total		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		$ 365,000,000

[1] For December 31, 2020, includes $365 million in loans originated under the Paycheck Protection Program.

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