Note 5 - Loans and Allowance for Loan Losses - Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired, Segregated by Class of Loans (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Unpaid Contractual Principal Balance	$ 55,752,000		$ 55,752,000		$ 54,521,000
Recorded Investment With No Allowance	31,223,000		31,223,000		24,678,000
Recorded Investment With Allowance	20,586,000		20,586,000		19,018,000
Impaired Financing Receivable, Recorded Investment	51,809,000		51,809,000		43,696,000
Impaired Financing Receivable, Related Allowance	6,321,000		6,321,000		680,000
Average Investment in Impaired Loans	54,468,000	$ 42,121,000	52,504,000	$ 34,048,000
Interest Income Recognized	350,000	430,000	1,050,000	1,230,000
Consumer Portfolio Segment [Member]
Unpaid Contractual Principal Balance	4,295,000		4,295,000		2,209,000
Recorded Investment With No Allowance	4,153,000		4,153,000		2,170,000
Recorded Investment With Allowance					3,000
Impaired Financing Receivable, Recorded Investment	4,153,000		4,153,000		2,173,000
Impaired Financing Receivable, Related Allowance					1,000
Average Investment in Impaired Loans	3,597,000	1,763,000	3,003,000	1,222,000
Interest Income Recognized	35,000	14,000	76,000	42,000
Consumer Portfolio Segment [Member] \| Credit Card Receivable [Member]
Unpaid Contractual Principal Balance	273,000		273,000		373,000
Recorded Investment With No Allowance	273,000		273,000		373,000
Recorded Investment With Allowance
Impaired Financing Receivable, Recorded Investment	273,000		273,000		373,000
Impaired Financing Receivable, Related Allowance
Average Investment in Impaired Loans	283,000	439,000	292,000	340,000
Interest Income Recognized	12,000		23,000	10,000
Consumer Portfolio Segment [Member] \| Other Loans [Member]
Unpaid Contractual Principal Balance	4,022,000		4,022,000		1,836,000
Recorded Investment With No Allowance	3,880,000		3,880,000		1,797,000
Recorded Investment With Allowance					3,000
Impaired Financing Receivable, Recorded Investment	3,880,000		3,880,000		1,800,000
Impaired Financing Receivable, Related Allowance					1,000
Average Investment in Impaired Loans	3,314,000	1,324,000	2,711,000	882,000
Interest Income Recognized	23,000	14,000	53,000	32,000
Commercial Real Estate Portfolio Segment [Member]
Unpaid Contractual Principal Balance	35,499,000		35,499,000		38,238,000
Recorded Investment With No Allowance	21,206,000		21,206,000		18,559,000
Recorded Investment With Allowance	12,474,000		12,474,000		11,442,000
Impaired Financing Receivable, Recorded Investment	33,680,000		33,680,000		30,001,000
Impaired Financing Receivable, Related Allowance	2,325,000		2,325,000		417,000
Average Investment in Impaired Loans	34,766,000	34,352,000	34,913,000	28,567,000
Interest Income Recognized	223,000	341,000	687,000	1,034,000
Commercial Real Estate Portfolio Segment [Member] \| Construction Loans [Member]
Unpaid Contractual Principal Balance	2,652,000		2,652,000		4,275,000
Recorded Investment With No Allowance	1,496,000		1,496,000		1,038,000
Recorded Investment With Allowance	907,000		907,000		2,374,000
Impaired Financing Receivable, Recorded Investment	2,403,000		2,403,000		3,412,000
Impaired Financing Receivable, Related Allowance	220,000		220,000		156,000
Average Investment in Impaired Loans	2,582,000	4,474,000	2,828,000	4,692,000
Interest Income Recognized	17,000	44,000	56,000	170,000
Commercial Real Estate Portfolio Segment [Member] \| Single Family Residential Loans [Member]
Unpaid Contractual Principal Balance	13,782,000		13,782,000		12,970,000
Recorded Investment With No Allowance	12,450,000		12,450,000		10,630,000
Recorded Investment With Allowance	584,000		584,000		1,753,000
Impaired Financing Receivable, Recorded Investment	13,034,000		13,034,000		12,383,000
Impaired Financing Receivable, Related Allowance	53,000		53,000		162,000
Average Investment in Impaired Loans	12,878,000	10,897,000	12,772,000	8,762,000
Interest Income Recognized	85,000	119,000	251,000	317,000
Commercial Real Estate Portfolio Segment [Member] \| Other Commercial Loans [Member]
Unpaid Contractual Principal Balance	19,065,000		19,065,000		20,993,000
Recorded Investment With No Allowance	7,260,000		7,260,000		6,891,000
Recorded Investment With Allowance	10,983,000		10,983,000		7,315,000
Impaired Financing Receivable, Recorded Investment	18,243,000		18,243,000		14,206,000
Impaired Financing Receivable, Related Allowance	2,052,000		2,052,000		99,000
Average Investment in Impaired Loans	19,306,000	18,981,000	19,313,000	15,113,000
Interest Income Recognized	121,000	178,000	380,000	547,000
Commercial Portfolio Segment [Member]
Unpaid Contractual Principal Balance	15,958,000		15,958,000		14,074,000
Recorded Investment With No Allowance	5,864,000		5,864,000		3,949,000
Recorded Investment With Allowance	8,112,000		8,112,000		7,573,000
Impaired Financing Receivable, Recorded Investment	13,976,000		13,976,000		11,522,000
Impaired Financing Receivable, Related Allowance	3,996,000		3,996,000		262,000
Average Investment in Impaired Loans	16,105,000	6,006,000	14,588,000	4,259,000
Interest Income Recognized	92,000	75,000	287,000	154,000
Commercial Portfolio Segment [Member] \| Commercial Loans [Member]
Unpaid Contractual Principal Balance	13,774,000		13,774,000		11,848,000
Recorded Investment With No Allowance	4,805,000		4,805,000		2,734,000
Recorded Investment With Allowance	8,112,000		8,112,000		7,573,000
Impaired Financing Receivable, Recorded Investment	12,917,000		12,917,000		10,307,000
Impaired Financing Receivable, Related Allowance	3,996,000		3,996,000		262,000
Average Investment in Impaired Loans	14,543,000	4,402,000	12,943,000	3,256,000
Interest Income Recognized	84,000	59,000	255,000	118,000
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member]
Unpaid Contractual Principal Balance	2,184,000		2,184,000		2,226,000
Recorded Investment With No Allowance	1,059,000		1,059,000		1,215,000
Recorded Investment With Allowance
Impaired Financing Receivable, Recorded Investment	1,059,000		1,059,000		1,215,000
Impaired Financing Receivable, Related Allowance
Average Investment in Impaired Loans	1,562,000	1,604,000	1,645,000	1,003,000
Interest Income Recognized	$ 8,000	$ 16,000	$ 32,000	$ 36,000

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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