Note 3 - Loans and Allowance for Loan Losses - Activity in Allowance for Loan Losses and the Recorded Investments in Loans (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021		Mar. 31, 2020	Dec. 31, 2020
Beginning balance	$ 37,967,000		$ 23,889,000
Provision for loan losses	300,000		750,000
Charge-offs	(52,000)		(40,000)
Recoveries	480,000		229,000
Ending balance	38,695,000		24,828,000
Ending balance: individually evaluated for impairment	487,000		1,612,000
Ending balance: collectively evaluated for impairment	38,208,000		23,216,000
Ending balance	2,909,799,000			$ 2,828,211,000
Ending balance: individually evaluated for impairment	22,837,000			26,958,000
Ending balance: collectively evaluated for impairment	2,886,962,000			2,801,253,000
Commercial Portfolio Segment [Member]
Beginning balance	33,779,000		21,070,000
Provision for loan losses	583,000		573,000
Charge-offs	(15,000)		(13,000)
Recoveries	364,000		120,000
Ending balance	34,711,000		21,750,000
Ending balance: individually evaluated for impairment	116,000		1,169,000
Ending balance: collectively evaluated for impairment	34,595,000		20,581,000
Ending balance	2,512,644,000	[1]		2,428,703,000	[2]
Ending balance: individually evaluated for impairment	18,486,000	[1]		22,415,000	[2]
Ending balance: collectively evaluated for impairment	2,494,158,000	[1]		2,406,288,000	[2]
Retail Portfolio Segment [Member]
Beginning balance	4,129,000		2,749,000
Provision for loan losses	(414,000)		247,000
Charge-offs	(37,000)		(27,000)
Recoveries	116,000		109,000
Ending balance	3,794,000		3,078,000
Ending balance: individually evaluated for impairment	371,000		443,000
Ending balance: collectively evaluated for impairment	3,423,000		2,635,000
Ending balance	397,155,000			399,508,000
Ending balance: individually evaluated for impairment	4,351,000			4,543,000
Ending balance: collectively evaluated for impairment	392,804,000			$ 394,965,000
Unallocated Financing Receivables [Member]
Beginning balance	59,000		70,000
Provision for loan losses	131,000		(70,000)
Charge-offs	0		0
Recoveries	0		0
Ending balance	190,000		0
Ending balance: individually evaluated for impairment	0		0
Ending balance: collectively evaluated for impairment	$ 190,000		$ 0

[1] Excludes $455 million in loans originated under the Paycheck Protection Program.

[2] Excludes $365 million in loans originated under the Paycheck Protection Program.