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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Provision for loan losses	$ 900,000	$ 700,000	$ 1,750,000	$ 700,000
Loans and Leases Receivable, Net of Deferred Income, Total	2,881,493,000		2,881,493,000		$ 2,753,085,000
Originated Loan [Member]
Beginning balance	22,418,000	19,081,000	21,554,000	19,133,000
Provision for loan losses	898,000	914,000	1,867,000	132,000
Charge-offs	(77,000)	(274,000)	(252,000)	(666,000)
Recoveries	92,000	761,000	162,000	1,883,000
Ending balance	23,331,000	20,482,000	23,331,000	20,482,000
Ending balance: individually evaluated for impairment	2,227,000	674,000	2,227,000	674,000
Ending balance: collectively evaluated for impairment	21,104,000	19,808,000	21,104,000	19,808,000
Loans and Leases Receivable, Net of Deferred Income, Total	2,609,686,000		2,609,686,000		2,452,446,000
Ending balance: individually evaluated for impairment	27,785,000		27,785,000		18,882,000
Ending balance: collectively evaluated for impairment	2,581,901,000		2,581,901,000		2,433,564,000
Acquired Loan [Member]
Beginning balance	717,000	893,000	826,000	368,000
Provision for loan losses	2,000	(214,000)	(117,000)	568,000
Charge-offs	0	0	0	(261,000)
Recoveries	3,000	6,000	13,000	10,000
Ending balance	722,000	685,000	722,000	685,000
Loans and Leases Receivable, Net of Deferred Income, Total	271,807,000		271,807,000		300,639,000
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income, Total	2,464,555,000		2,464,555,000		2,360,106,000
Commercial Portfolio Segment [Member] | Originated Loan [Member]
Beginning balance	20,050,000	16,865,000	19,442,000	16,456,000
Provision for loan losses	979,000	892,000	1,559,000	551,000
Charge-offs	(2,000)	(85,000)	(2,000)	(342,000)
Recoveries	46,000	654,000	74,000	1,661,000
Ending balance	21,073,000	18,326,000	21,073,000	18,326,000
Ending balance: individually evaluated for impairment	2,051,000	391,000	2,051,000	391,000
Ending balance: collectively evaluated for impairment	19,022,000	17,935,000	19,022,000	17,935,000
Loans and Leases Receivable, Net of Deferred Income, Total	2,274,931,000		2,274,931,000		2,151,998,000
Ending balance: individually evaluated for impairment	25,936,000		25,936,000		17,134,000
Ending balance: collectively evaluated for impairment	2,248,995,000		2,248,995,000		2,134,864,000
Commercial Portfolio Segment [Member] | Acquired Loan [Member]
Beginning balance	161,000	359,000	177,000	291,000
Provision for loan losses	36,000	(254,000)	20,000	60,000
Charge-offs	0	0	0	(246,000)
Recoveries	1,000	0	1,000	0
Ending balance	198,000	105,000	198,000	105,000
Loans and Leases Receivable, Net of Deferred Income, Total	189,624,000		189,624,000		208,108,000
Retail Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income, Total	416,938,000		416,938,000		392,979,000
Retail Portfolio Segment [Member] | Originated Loan [Member]
Beginning balance	2,140,000	2,001,000	2,068,000	2,584,000
Provision for loan losses	50,000	297,000	255,000	(266,000)
Charge-offs	(75,000)	(189,000)	(250,000)	(324,000)
Recoveries	46,000	107,000	88,000	222,000
Ending balance	2,161,000	2,216,000	2,161,000	2,216,000
Ending balance: individually evaluated for impairment	176,000	283,000	176,000	283,000
Ending balance: collectively evaluated for impairment	1,985,000	1,933,000	1,985,000	1,933,000
Loans and Leases Receivable, Net of Deferred Income, Total	334,755,000		334,755,000		300,448,000
Ending balance: individually evaluated for impairment	1,849,000		1,849,000		1,748,000
Ending balance: collectively evaluated for impairment	332,906,000		332,906,000		298,700,000
Retail Portfolio Segment [Member] | Acquired Loan [Member]
Beginning balance	556,000	534,000	649,000	77,000
Provision for loan losses	(34,000)	40,000	(137,000)	508,000
Charge-offs	0	0	0	(15,000)
Recoveries	2,000	6,000	12,000	10,000
Ending balance	524,000	580,000	524,000	580,000
Loans and Leases Receivable, Net of Deferred Income, Total	82,183,000		82,183,000		$ 92,531,000
Unallocated Financing Receivables [Member] | Originated Loan [Member]
Beginning balance	228,000	215,000	44,000	93,000
Provision for loan losses	(131,000)	(275,000)	53,000	(153,000)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	97,000	(60,000)	97,000	(60,000)
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	97,000	(60,000)	97,000	(60,000)
Loans and Leases Receivable, Net of Deferred Income, Total
Unallocated Financing Receivables [Member] | Acquired Loan [Member]
Beginning balance	0	0	0	0
Provision for loan losses	0	0	0	0
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	$ 0	$ 0	$ 0	$ 0