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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Provision for loan losses	$ 1,000,000	$ 600,000	$ 2,350,000	$ 2,300,000
Loans and Leases Receivable, Net of Deferred Income	2,554,272,000		2,554,272,000		$ 2,378,620,000
Originated Loan [Member]
Beginning balance	17,955,000	16,876,000	17,868,000	15,233,000
Provision for loan losses	913,000	570,000	2,023,000	2,399,000
Charge-offs	(667,000)	(291,000)	(2,262,000)	(1,163,000)
Recoveries	606,000	179,000	1,178,000	865,000
Ending balance	18,807,000	17,334,000	18,807,000	17,334,000
Ending balance: individually evaluated for impairment	2,594,000	1,040,000	2,594,000	1,040,000
Ending balance: collectively evaluated for impairment	16,213,000	16,294,000	16,213,000	16,294,000
Loans and Leases Receivable, Net of Deferred Income	2,133,766,000		2,133,766,000		1,884,548,000
Ending balance: individually evaluated for impairment	10,877,000		10,877,000		13,383,000
Ending balance: collectively evaluated for impairment	2,122,889,000		2,122,889,000		1,871,165,000
Acquired Loan [Member]
Beginning balance	340,000	234,000	93,000	448,000
Provision for loan losses	87,000	30,000	327,000	(99,000)
Charge-offs	(42,000)	(72,000)	(53,000)	(72,000)
Recoveries	1,000	0	19,000
Recoveries				(85,000)
Ending balance	386,000	192,000	386,000	192,000
Loans and Leases Receivable, Net of Deferred Income	420,506,000		420,506,000		494,072,000
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income	2,214,822,000		2,214,822,000		2,065,347,000
Commercial Portfolio Segment [Member] | Originated Loan [Member]
Beginning balance	15,363,000	14,729,000	16,026,000	13,672,000
Provision for loan losses	452,000	493,000	600,000	1,429,000
Charge-offs	(347,000)	(1,000)	(1,579,000)	(256,000)
Recoveries	565,000	78,000	986,000	454,000
Ending balance	16,033,000	15,299,000	16,033,000	15,299,000
Ending balance: individually evaluated for impairment	1,856,000	754,000	1,856,000	754,000
Ending balance: collectively evaluated for impairment	14,177,000	14,545,000	14,177,000	14,545,000
Loans and Leases Receivable, Net of Deferred Income	1,922,998,000		1,922,998,000		1,728,898,000
Ending balance: individually evaluated for impairment	8,320,000		8,320,000		12,070,000
Ending balance: collectively evaluated for impairment	1,914,678,000		1,914,678,000		1,716,828,000
Commercial Portfolio Segment [Member] | Acquired Loan [Member]
Beginning balance	324,000	211,000	75,000	420,000
Provision for loan losses	(18,000)	(39,000)	224,000	(206,000)
Charge-offs	(1,000)	0	(12,000)	0
Recoveries	1,000	0	19,000
Recoveries				(42,000)
Ending balance	306,000	172,000	306,000	172,000
Loans and Leases Receivable, Net of Deferred Income	291,824,000		291,824,000		336,449,000
Retail Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income	339,450,000		339,450,000		313,273,000
Retail Portfolio Segment [Member] | Originated Loan [Member]
Beginning balance	2,433,000	1,913,000	1,882,000	1,421,000
Provision for loan losses	415,000	329,000	1,178,000	1,128,000
Charge-offs	(320,000)	(290,000)	(683,000)	(907,000)
Recoveries	41,000	101,000	192,000	411,000
Ending balance	2,569,000	2,053,000	2,569,000	2,053,000
Ending balance: individually evaluated for impairment	738,000	286,000	738,000	286,000
Ending balance: collectively evaluated for impairment	1,831,000	1,767,000	1,831,000	1,767,000
Loans and Leases Receivable, Net of Deferred Income	210,768,000		210,768,000		155,650,000
Ending balance: individually evaluated for impairment	2,557,000		2,557,000		1,313,000
Ending balance: collectively evaluated for impairment	208,211,000		208,211,000		154,337,000
Retail Portfolio Segment [Member] | Acquired Loan [Member]
Beginning balance	16,000	23,000	18,000	28,000
Provision for loan losses	105,000	69,000	103,000	107,000
Charge-offs	(41,000)	(72,000)	(41,000)	(72,000)
Recoveries	0	0	0
Recoveries				(43,000)
Ending balance	80,000	20,000	80,000	20,000
Loans and Leases Receivable, Net of Deferred Income	128,682,000		128,682,000		157,623,000
Unallocated Financing Receivables [Member] | Originated Loan [Member]
Beginning balance	159,000	234,000	(40,000)	140,000
Provision for loan losses	46,000	(252,000)	245,000	(158,000)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	205,000	(18,000)	205,000	(18,000)
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	205,000	(18,000)	205,000	(18,000)
Loans and Leases Receivable, Net of Deferred Income
Ending balance: individually evaluated for impairment
Ending balance: collectively evaluated for impairment
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
Recoveries				0
Ending balance	$ 0	$ 0	$ 0	$ 0