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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Provision for loan losses	$ 750,000	$ 1,100,000	$ 1,350,000	$ 1,700,000
Loans and Leases Receivable, Net of Deferred Income	2,527,281,000		2,527,281,000		$ 2,378,620,000
Originated Loan [Member]
Beginning balance	18,126,000	15,972,000	17,868,000	15,233,000
Provision for loan losses	562,000	1,158,000	1,110,000	1,829,000
Charge-offs	(1,150,000)	(397,000)	(1,595,000)	(872,000)
Recoveries	417,000	143,000	572,000	686,000
Ending balance	17,955,000	16,876,000	17,955,000	16,876,000
Ending balance: collectively evaluated for impairment	15,156,000	15,840,000	15,156,000	15,840,000
Loans and Leases Receivable, Net of Deferred Income	2,078,875,000		2,078,875,000		1,884,548,000
Ending balance: individually evaluated for impairment	10,413,000		10,413,000		13,383,000
Ending balance: collectively evaluated for impairment	2,068,462,000		2,068,462,000		1,871,165,000
Ending balance: individually evaluated for impairment	2,799,000	1,036,000	2,799,000	1,036,000
Acquired Loan [Member]
Beginning balance	150,000	290,000	93,000	448,000
Provision for loan losses	188,000	(58,000)	240,000	(129,000)
Charge-offs	0	0	(11,000)	0
Recoveries	2,000	2,000	18,000
Recoveries				(85,000)
Ending balance	340,000	234,000	340,000	234,000
Loans and Leases Receivable, Net of Deferred Income	448,406,000		448,406,000		494,072,000
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income	2,198,593,000		2,198,593,000		2,065,347,000
Commercial Portfolio Segment [Member] | Originated Loan [Member]
Beginning balance	15,671,000	13,924,000	16,026,000	13,672,000
Provision for loan losses	372,000	842,000	147,000	936,000
Charge-offs	(1,006,000)	(166,000)	(1,231,000)	(255,000)
Recoveries	326,000	129,000	421,000	376,000
Ending balance	15,363,000	14,729,000	15,363,000	14,729,000
Ending balance: collectively evaluated for impairment	13,319,000	13,902,000	13,319,000	13,902,000
Loans and Leases Receivable, Net of Deferred Income	1,888,130,000		1,888,130,000		1,728,898,000
Ending balance: individually evaluated for impairment	7,989,000		7,989,000		12,070,000
Ending balance: collectively evaluated for impairment	1,880,141,000		1,880,141,000		1,716,828,000
Ending balance: individually evaluated for impairment	2,044,000	827,000	2,044,000	827,000
Commercial Portfolio Segment [Member] | Acquired Loan [Member]
Beginning balance	125,000	266,000	75,000	420,000
Provision for loan losses	197,000	(57,000)	242,000	(167,000)
Charge-offs	0	0	(11,000)	0
Recoveries	2,000	2,000	18,000
Recoveries				(42,000)
Ending balance	324,000	211,000	324,000	211,000
Loans and Leases Receivable, Net of Deferred Income	310,463,000		310,463,000		336,449,000
Retail Portfolio Segment [Member]
Loans and Leases Receivable, Net of Deferred Income	328,688,000		328,688,000		313,273,000
Retail Portfolio Segment [Member] | Originated Loan [Member]
Beginning balance	2,365,000	1,834,000	1,882,000	1,421,000
Provision for loan losses	121,000	296,000	764,000	799,000
Charge-offs	(144,000)	(231,000)	(364,000)	(617,000)
Recoveries	91,000	14,000	151,000	310,000
Ending balance	2,433,000	1,913,000	2,433,000	1,913,000
Ending balance: collectively evaluated for impairment	1,678,000	1,704,000	1,678,000	1,704,000
Loans and Leases Receivable, Net of Deferred Income	190,745,000		190,745,000		155,650,000
Ending balance: individually evaluated for impairment	2,424,000		2,424,000		1,313,000
Ending balance: collectively evaluated for impairment	188,321,000		188,321,000		154,337,000
Ending balance: individually evaluated for impairment	755,000	209,000	755,000	209,000
Retail Portfolio Segment [Member] | Acquired Loan [Member]
Beginning balance	25,000	24,000	18,000	28,000
Provision for loan losses	(9,000)	(1,000)	(2,000)	38,000
Charge-offs	0	0	0	0
Recoveries	0	0	0
Recoveries				(43,000)
Ending balance	16,000	23,000	16,000	23,000
Loans and Leases Receivable, Net of Deferred Income	137,943,000		137,943,000		157,623,000
Unallocated Financing Receivables [Member] | Originated Loan [Member]
Beginning balance	90,000	214,000	(40,000)	140,000
Provision for loan losses	69,000	20,000	199,000	94,000
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	159,000	234,000	159,000	234,000
Ending balance: collectively evaluated for impairment	159,000	234,000	159,000	234,000
Loans and Leases Receivable, Net of Deferred Income
Ending balance: individually evaluated for impairment
Ending balance: collectively evaluated for impairment
Ending balance: individually evaluated for impairment	0	0	0	0
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