Note 5 - Allowance for Loan and Lease Losses - Allowance for Loan and Lease Losses by Loan Category (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance				$ 8,202,710				$ 7,809,700	$ 8,202,710	$ 7,809,700	$ 7,873,790
Loans charged off									(344,888)	(702,557)	(1,316,082)
Recoveries									181,537	249,110	126,585
Provision for credit losses	$ 200,000	$ 220,000	$ 325,000	225,000	$ 325,000	$ 335,000	$ 140,000		970,000	800,000	1,100,000
Balance	8,984,795				8,202,710				8,984,795	8,202,710	7,809,700
Credit exposure by assigned risk grade	701,443,000				607,865,000				701,443,000	607,865,000
Allowance for Loans and Leases Receivable [Member]
Balance				7,867,000				7,520,000	7,867,000	7,520,000
Loans charged off									(345,000)	(702,000)
Recoveries									181,000	249,000
Provision for credit losses									970,000	800,000
Balance	8,673,000				7,867,000				8,673,000	7,867,000	7,520,000
Credit exposure by assigned risk grade	701,443,000				607,865,000				701,443,000	607,865,000
Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				7,249,000				6,728,000	7,249,000	6,728,000
Loans charged off									(127,000)	(145,000)
Recoveries									156,000	170,000
Provision for credit losses									1,002,000	496,000
Balance	8,280,000				7,249,000				8,280,000	7,249,000	6,728,000
Credit exposure by assigned risk grade	690,320,000				592,045,000				690,320,000	592,045,000
Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				618,000				792,000	618,000	792,000
Loans charged off									(218,000)	(557,000)
Recoveries									25,000	79,000
Provision for credit losses									(32,000)	304,000
Balance	393,000				618,000				393,000	618,000	792,000
Credit exposure by assigned risk grade	11,123,000				15,820,000				11,123,000	15,820,000
Residential Portfolio Segment [Member]
Credit exposure by assigned risk grade	75,293,000				72,320,000				75,293,000	72,320,000
Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans charged off									(2,000)	(301,000)
Recoveries									3,000	1,000
Credit exposure by assigned risk grade	67,264,000				68,229,000				67,264,000	68,229,000
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				730,000				982,000	730,000	982,000
Loans charged off									0	(116,000)
Recoveries
Provision for credit losses									(35,000)	(136,000)
Balance	695,000				730,000				695,000	730,000	982,000
Credit exposure by assigned risk grade	66,667,000				67,142,000				66,667,000	67,142,000
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				0				185,000	0	185,000
Loans charged off									(2,000)	(185,000)
Recoveries									3,000	1,000
Provision for credit losses									(1,000)	(1,000)
Balance					0					0	185,000
Credit exposure by assigned risk grade	597,000				1,087,000				597,000	1,087,000
Residential Portfolio Segment [Member] | Construction Loans [Member]
Credit exposure by assigned risk grade	7,875,000				3,934,000				7,875,000	3,934,000
Residential Portfolio Segment [Member] | Construction Loans [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				47,000				17,000	47,000	17,000
Loans charged off									0	0
Recoveries
Provision for credit losses									42,000	30,000
Balance	89,000				47,000				89,000	47,000	17,000
Credit exposure by assigned risk grade	7,875,000				3,934,000				7,875,000	3,934,000
Residential Portfolio Segment [Member] | Lots and Raw Land [Member]
Credit exposure by assigned risk grade	154,000				157,000				154,000	157,000
Residential Portfolio Segment [Member] | Lots and Raw Land [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				2,000				11,000	2,000	11,000
Loans charged off									0	0
Recoveries
Provision for credit losses										(9,000)
Balance	2,000				2,000				2,000	2,000	11,000
Credit exposure by assigned risk grade	154,000				157,000				154,000	157,000
Residential Portfolio Segment [Member] | Lease Receivables [Member]
Credit exposure by assigned risk grade	21,236,000				17,235,000				21,236,000	17,235,000
Commercial Portfolio Segment [Member]
Credit exposure by assigned risk grade	556,941,000				472,688,000				556,941,000	472,688,000
Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans charged off									(101,000)	(172,000)
Recoveries									35,000	83,000
Credit exposure by assigned risk grade	378,173,000				338,714,000				378,173,000	338,714,000
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				4,065,000				3,516,000	4,065,000	3,516,000
Loans charged off									(33,000)	(3,000)
Recoveries									32,000	48,000
Provision for credit losses									498,000	504,000
Balance	4,562,000				4,065,000				4,562,000	4,065,000	3,516,000
Credit exposure by assigned risk grade	371,305,000				328,372,000				371,305,000	328,372,000
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				0				167,000	0	167,000
Loans charged off									(68,000)	(169,000)
Recoveries									3,000	35,000
Provision for credit losses									65,000	(33,000)
Balance					0					0	167,000
Credit exposure by assigned risk grade	6,868,000				10,342,000				6,868,000	10,342,000
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans charged off
Recoveries									70,000
Credit exposure by assigned risk grade	56,118,000				42,987,000				56,118,000	42,987,000
Commercial Portfolio Segment [Member] | Lots and Raw Land [Member]
Loans charged off										(33,000)
Recoveries									11,000	4,000
Credit exposure by assigned risk grade	33,434,000				28,271,000				33,434,000	28,271,000
Commercial Portfolio Segment [Member] | Lots and Raw Land [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				303,000				377,000	303,000	377,000
Loans charged off									0	0
Recoveries
Provision for credit losses									62,000	(74,000)
Balance	365,000				303,000				365,000	303,000	377,000
Credit exposure by assigned risk grade	31,249,000				25,655,000				31,249,000	25,655,000
Commercial Portfolio Segment [Member] | Lots and Raw Land [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				365,000				251,000	365,000	251,000
Loans charged off									0	(33,000)
Recoveries									11,000
Provision for credit losses									(376,000)	147,000
Balance					365,000					365,000	251,000
Credit exposure by assigned risk grade	2,185,000				2,616,000				2,185,000	2,616,000
Commercial Portfolio Segment [Member] | Commercial Construction [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				518,000				375,000	518,000	375,000
Loans charged off									0	0
Recoveries									70,000
Provision for credit losses									101,000	143,000
Balance	689,000				518,000				689,000	518,000	375,000
Credit exposure by assigned risk grade	56,118,000				42,413,000				56,118,000	42,413,000
Commercial Portfolio Segment [Member] | Commercial Construction [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance								0		0
Loans charged off										0
Recoveries
Provision for credit losses
Balance											0
Credit exposure by assigned risk grade					574,000					574,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Loans charged off									(2,000)
Recoveries									13,000
Credit exposure by assigned risk grade	67,980,000				45,481,000				67,980,000	45,481,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				641,000				400,000	641,000	400,000
Loans charged off									(2,000)	0
Recoveries									13,000	4,000
Provision for credit losses									188,000	237,000
Balance	840,000				641,000				840,000	641,000	400,000
Credit exposure by assigned risk grade	67,636,000				45,425,000				67,636,000	45,425,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				14,000				0	14,000	0
Loans charged off									0	0
Recoveries
Provision for credit losses									212,000	14,000
Balance	226,000				14,000				226,000	14,000	0
Credit exposure by assigned risk grade	344,000				56,000				344,000	56,000
Commercial Portfolio Segment [Member] | Lease Receivables [Member]
Loans charged off
Credit exposure by assigned risk grade	21,236,000				17,235,000				21,236,000	17,235,000
Commercial Portfolio Segment [Member] | Lease Receivables [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				196,000				172,000	196,000	172,000
Loans charged off									0	0
Recoveries
Provision for credit losses									30,000	24,000
Balance	226,000				196,000				226,000	196,000	172,000
Credit exposure by assigned risk grade	21,236,000				17,235,000				21,236,000	17,235,000
Consumer Portfolio Segment [Member]
Credit exposure by assigned risk grade	69,209,000				62,857,000				69,209,000	62,857,000
Consumer Portfolio Segment [Member] | Real Estate Loan [Member]
Loans charged off									(81,000)	(85,000)
Recoveries									13,000	18,000
Credit exposure by assigned risk grade	16,967,000				17,239,000				16,967,000	17,239,000
Consumer Portfolio Segment [Member] | Real Estate Loan [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				198,000				250,000	198,000	250,000
Loans charged off									(6,000)	0
Recoveries									13,000	18,000
Provision for credit losses									(19,000)	(70,000)
Balance	186,000				198,000				186,000	198,000	250,000
Credit exposure by assigned risk grade	16,746,000				16,959,000				16,746,000	16,959,000
Consumer Portfolio Segment [Member] | Real Estate Loan [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				30,000				19,000	30,000	19,000
Loans charged off									(75,000)	(85,000)
Recoveries
Provision for credit losses									45,000	96,000
Balance					30,000					30,000	19,000
Credit exposure by assigned risk grade	221,000				280,000				221,000	280,000
Consumer Portfolio Segment [Member] | Construction Loans [Member]
Credit exposure by assigned risk grade	105,000				196,000				105,000	196,000
Consumer Portfolio Segment [Member] | Construction Loans [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				2,000				19,000	2,000	19,000
Loans charged off									0	0
Recoveries
Provision for credit losses									(1,000)	(17,000)
Balance	1,000				2,000				1,000	2,000	19,000
Credit exposure by assigned risk grade	105,000				196,000				105,000	196,000
Consumer Portfolio Segment [Member] | Lots and Raw Land [Member]
Loans charged off									(78,000)	(85,000)
Recoveries									2,000	8,000
Credit exposure by assigned risk grade	8,975,000				9,643,000				8,975,000	9,643,000
Consumer Portfolio Segment [Member] | Lots and Raw Land [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				125,000				152,000	125,000	152,000
Loans charged off									(5,000)	0
Recoveries
Provision for credit losses									13,000	(27,000)
Balance	133,000				125,000				133,000	125,000	152,000
Credit exposure by assigned risk grade	8,199,000				8,870,000				8,199,000	8,870,000
Consumer Portfolio Segment [Member] | Lots and Raw Land [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				209,000				165,000	209,000	165,000
Loans charged off									(73,000)	(85,000)
Recoveries									2,000	8,000
Provision for credit losses									6,000	121,000
Balance	144,000				209,000				144,000	209,000	165,000
Credit exposure by assigned risk grade	776,000				773,000				776,000	773,000
Consumer Portfolio Segment [Member] | Lease Receivables [Member]
Credit exposure by assigned risk grade	8,975,000				9,643,000				8,975,000	9,643,000
Consumer Portfolio Segment [Member] | Home Equity Loan [Member]
Loans charged off									(23,000)	(13,000)
Recoveries									7,000	36,000
Credit exposure by assigned risk grade	36,815,000				29,709,000				36,815,000	29,709,000
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				351,000				405,000	351,000	405,000
Loans charged off									(23,000)	(13,000)
Recoveries									1,000	1,000
Provision for credit losses									86,000	(42,000)
Balance	415,000				351,000				415,000	351,000	405,000
Credit exposure by assigned risk grade	36,721,000				29,659,000				36,721,000	29,659,000
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				0				5,000	0	5,000
Loans charged off									0	0
Recoveries									6,000	35,000
Provision for credit losses									17,000	(40,000)
Balance	23,000				0				23,000	0	5,000
Credit exposure by assigned risk grade	94,000				50,000				94,000	50,000
Consumer Portfolio Segment [Member] | Other Loans [Member]
Loans charged off									(58,000)	(13,000)
Recoveries									27,000	99,000
Credit exposure by assigned risk grade	6,347,000				6,070,000				6,347,000	6,070,000
Consumer Portfolio Segment [Member] | Other Loans [Member] | Total Collectively Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				71,000				52,000	71,000	52,000
Loans charged off									(58,000)	(13,000)
Recoveries									27,000	99,000
Provision for credit losses									37,000	(67,000)
Balance	77,000				71,000				77,000	71,000	52,000
Credit exposure by assigned risk grade	6,309,000				6,028,000				6,309,000	6,028,000
Consumer Portfolio Segment [Member] | Other Loans [Member] | Total Individually Evaluated [Member] | Allowance for Loans and Leases Receivable [Member]
Balance				$ 0				$ 0	0	0
Loans charged off									0	0
Recoveries
Provision for credit losses
Balance					0					0	$ 0
Credit exposure by assigned risk grade	$ 38,000				$ 42,000				$ 38,000	$ 42,000