Note 4 - Loans and Allowance for Loan Losses - Activity in Allowance for Loan Losses and the Recorded Investments in Loans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Provision for loan losses	$ 2,900,000	$ (1,000,000)	$ (3,000,000)
Loans	2,378,620,000	2,277,727,000
Commercial Portfolio Segment [Member]
Loans	2,065,347,000	1,946,696,000
Retail Portfolio Segment [Member]
Loans	313,273,000	331,031,000
Originated Loan [Member]
Beginning balance	15,233,000	19,299,000	22,821,000
Provision for loan losses	3,098,000	(701,000)	(3,793,000)
Charge-offs	(2,133,000)	(6,195,000)	(1,430,000)
Recoveries	1,670,000	2,830,000	1,701,000
Ending balance	17,868,000	15,233,000	19,299,000
Ending balance: individually evaluated for impairment	1,572,000	1,474,000	10,152,000
Ending balance: collectively evaluated for impairment	16,296,000	13,759,000	9,147,000
Loans	1,884,548,000	1,616,587,000	1,246,116,000
Ending balance: individually evaluated for impairment	13,383,000	18,197,000	47,856,000
Ending balance: collectively evaluated for impairment	1,871,165,000	1,598,390,000	1,198,260,000
Originated Loan [Member] | Commercial Portfolio Segment [Member]
Beginning balance	13,672,000	17,736,000	20,455,000
Provision for loan losses	2,247,000	(1,771,000)	(3,140,000)
Charge-offs	(980,000)	(4,915,000)	(876,000)
Recoveries	1,087,000	2,622,000	1,297,000
Ending balance	16,026,000	13,672,000	17,736,000
Ending balance: individually evaluated for impairment	1,303,000	1,218,000	9,374,000
Ending balance: collectively evaluated for impairment	14,723,000	12,454,000	8,362,000
Loans	1,728,898,000	1,493,516,000	1,153,189,000
Ending balance: individually evaluated for impairment	12,070,000	16,845,000	45,021,000
Ending balance: collectively evaluated for impairment	1,716,828,000	1,476,671,000	1,108,168,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
Beginning balance	1,421,000	1,487,000	2,358,000
Provision for loan losses	1,031,000	1,006,000	(721,000)
Charge-offs	(1,153,000)	(1,280,000)	(554,000)
Recoveries	583,000	208,000	404,000
Ending balance	1,882,000	1,421,000	1,487,000
Ending balance: individually evaluated for impairment	269,000	256,000	778,000
Ending balance: collectively evaluated for impairment	1,613,000	1,165,000	709,000
Loans	155,650,000	123,071,000	92,927,000
Ending balance: individually evaluated for impairment	1,313,000	1,352,000	2,835,000
Ending balance: collectively evaluated for impairment	154,337,000	121,719,000	90,092,000
Originated Loan [Member] | Unallocated Financing Receivables [Member]
Beginning balance	140,000	76,000	8,000
Provision for loan losses	(180,000)	64,000	68,000
Charge-offs	0	0	0
Recoveries	0	0	0
Ending balance	(40,000)	140,000	76,000
Ending balance: individually evaluated for impairment	0	0	0
Ending balance: collectively evaluated for impairment	(40,000)	140,000	76,000
Acquired Loan [Member]
Beginning balance	448,000	742,000	0
Provision for loan losses	(198,000)	(299,000)	793,000
Charge-offs	(72,000)	(84,000)	(71,000)
Recoveries	(85,000)	89,000	20,000
Ending balance	93,000	448,000	742,000
Loans	494,072,000	661,140,000
Acquired Loan [Member] | Commercial Portfolio Segment [Member]
Beginning balance	420,000	738,000	0
Provision for loan losses	(303,000)	(286,000)	791,000
Charge-offs	0	(77,000)	(55,000)
Recoveries	(42,000)	45,000	2,000
Ending balance	75,000	420,000	738,000
Loans	336,449,000	453,180,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
Beginning balance	28,000	4,000	0
Provision for loan losses	105,000	(13,000)	2,000
Charge-offs	(72,000)	(7,000)	(16,000)
Recoveries	(43,000)	44,000	18,000
Ending balance	18,000	28,000	4,000
Loans	157,623,000	207,960,000
Acquired Loan [Member] | Unallocated Financing Receivables [Member]
Beginning balance	0	0	0
Provision for loan losses	0	0	0
Charge-offs	0	0	0
Recoveries	0	0	0
Ending balance	$ 0	$ 0	$ 0