Note 5 - Credit Quality (Details Textual) $ in Thousands		12 Months Ended
		Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Collectively Evaluated for Impairment		$ 2,138,921		$ 1,672,634
Loans Deemed to be Impaired, Threshold					$ 500	$ 250
Impaired Financing Receivable, Recorded Investment, Total	[1]	39,225		31,172
Restructured Loans, Reserves		$ 500
Performing Status Returned Period (Month)		6 months
Financing Receivable, Troubled Debt Restructuring		$ 12,062		8,917
Financing Receivable, Number of Payment Deferrals		3,625
Financing Receivable, Deferred Payments		$ 458,170	$ 436,110
Commercial Portfolio Segment [Member]
Financing Receivable, Collectively Evaluated for Impairment		1,252,765		969,838
Financing Receivable, Deferred Payments		26,540
Consumer Portfolio Segment [Member]
Financing Receivable, Deferred Payments		5,720
Financial Asset Acquired with Credit Deterioration [Member]
Impaired Financing Receivable, Recorded Investment, Total		0		0
Impaired Loans [Member]
Financing Receivable, Collectively Evaluated for Impairment		31,180		24,640
Non-covered Loans [Member]
Financing Receivable, 90 Days or More Past Due, Still Accruing		295		144
Covered Loans [Member]
Financing Receivable, Troubled Debt Restructuring		$ 0		$ 0

[1] Total impaired loans include loans totaling $31.18 million as of December 31, 2020, and $24.64 million as of December 31, 2019, that do not meet the Company's evaluation threshold for individual impairment and are therefore collectively evaluated for impairment. During the first quarter of 2018, the Company changed the threshold for quarterly reviews of individual loans that are deemed to be impaired from $250 thousand to $500 thousand or greater.