Note 3 - Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance, beginning of year				$ 5,742,449				$ 5,812,000	$ 5,742,449	$ 5,812,000	$ 6,589,000
Provision for Loan Losses	$ 250,000	$ 450,000	$ 575,000	475,000	$ 425,000	$ 200,000	$ 375,000	375,000	1,750,000	1,375,000	600,000
Losses charged off									(536,000)	(1,699,000)	(1,451,000)
Recoveries									151,000	254,000	74,000
Balance, end of year	7,107,418				5,742,449				7,107,418	5,742,449	5,812,000
Ending balance: individually evaluated for impairment	1,249,000				602,000				1,249,000	602,000	865,000
Ending balance: collectively evaluated for impairment	5,858,000				5,140,000				5,858,000	5,140,000	4,947,000
Ending balance: individually evaluated for impairment	10,827,000				8,699,000				10,827,000	8,699,000	14,730,000
Ending balance: collectively evaluated for impairment	626,548,000				535,699,000				626,548,000	535,699,000	482,417,000
Real Estate, Construction [Member]
Balance, beginning of year				1,377,000				1,246,000	1,377,000	1,246,000	1,330,000
Provision for Loan Losses									793,000	1,262,000	1,139,000
Losses charged off										(1,222,000)	(1,233,000)
Recoveries									74,000	91,000	10,000
Balance, end of year	2,244,000				1,377,000				2,244,000	1,377,000	1,246,000
Ending balance: individually evaluated for impairment	738,000				302,000				738,000	302,000	540,000
Ending balance: collectively evaluated for impairment	1,506,000				1,075,000				1,506,000	1,075,000	706,000
Ending balance: individually evaluated for impairment	4,452,000				5,447,000				4,452,000	5,447,000	8,080,000
Ending balance: collectively evaluated for impairment	60,292,000				35,465,000				60,292,000	35,465,000	37,383,000
Commercial Real Estate Portfolio Segment [Member]
Balance, beginning of year				1,687,000				1,526,000	1,687,000	1,526,000	1,992,000
Provision for Loan Losses									174,000		(466,000)
Losses charged off									(72,000)
Recoveries
Balance, end of year	1,789,000				1,687,000				1,789,000	1,687,000	1,526,000
Ending balance: individually evaluated for impairment
Ending balance: collectively evaluated for impairment	1,789,000								1,789,000		1,526,000
Ending balance: individually evaluated for impairment	161,000								161,000		1,241,000
Ending balance: collectively evaluated for impairment	261,705,000								261,705,000		207,583,000
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Balance, beginning of year				1,687,000				1,526,000	1,687,000	1,526,000
Provision for Loan Losses										198,000
Losses charged off										(69,000)
Recoveries										32,000
Balance, end of year					1,687,000					1,687,000	1,526,000
Ending balance: individually evaluated for impairment					0					0
Ending balance: collectively evaluated for impairment					1,687,000					1,687,000
Ending balance: individually evaluated for impairment					161,000					161,000
Ending balance: collectively evaluated for impairment					249,420,000					249,420,000
Residential Portfolio Segment [Member] | Real Estate Residential, One To Four Family Units [Member]
Balance, beginning of year				856,000				821,000	856,000	821,000	900,000
Provision for Loan Losses									82,000	48,000
Losses charged off									(11,000)	(47,000)	(99,000)
Recoveries									19,000	34,000	20,000
Balance, end of year	946,000				856,000				946,000	856,000	821,000
Ending balance: individually evaluated for impairment	127,000				14,000				127,000	14,000
Ending balance: collectively evaluated for impairment	819,000				842,000				819,000	842,000	821,000
Ending balance: individually evaluated for impairment	4,424,000				2,060,000				4,424,000	2,060,000	2,272,000
Ending balance: collectively evaluated for impairment	101,877,000				104,351,000				101,877,000	104,351,000	95,985,000
Residential Portfolio Segment [Member] | Real Estate Residential, Multi Family Units [Member]
Balance, beginning of year				206,000				177,000	206,000	177,000	127,000
Provision for Loan Losses									258,000	29,000	50,000
Losses charged off									0	0	0
Recoveries									0	0	0
Balance, end of year	464,000				206,000				464,000	206,000	177,000
Ending balance: individually evaluated for impairment					0					0
Ending balance: collectively evaluated for impairment	464,000				206,000				464,000	206,000	177,000
Ending balance: individually evaluated for impairment	775,000				0				775,000	0
Ending balance: collectively evaluated for impairment	84,450,000				48,483,000				84,450,000	48,483,000	41,604,000
Commercial Portfolio Segment [Member]
Balance, beginning of year				1,168,000				1,382,000	1,168,000	1,382,000	1,954,000
Provision for Loan Losses									91,000	(51,000)	(576,000)
Losses charged off									(240,000)	(171,000)
Recoveries									12,000	8,000	4,000
Balance, end of year	1,031,000				1,168,000				1,031,000	1,168,000	1,382,000
Ending balance: individually evaluated for impairment	246,000				241,000				246,000	241,000	312,000
Ending balance: collectively evaluated for impairment	785,000				927,000				785,000	927,000	1,070,000
Ending balance: individually evaluated for impairment	739,000				925,000				739,000	925,000	2,149,000
Ending balance: collectively evaluated for impairment	93,784,000				74,480,000				93,784,000	74,480,000	78,858,000
Consumer and Other Loans [Member]
Balance, beginning of year				337,000				223,000	337,000	223,000	185,000
Provision for Loan Losses									284,000	215,000	117,000
Losses charged off									(213,000)	(190,000)	(119,000)
Recoveries									46,000	89,000	40,000
Balance, end of year	454,000				337,000				454,000	337,000	223,000
Ending balance: individually evaluated for impairment	138,000				45,000				138,000	45,000	13,000
Ending balance: collectively evaluated for impairment	316,000				292,000				316,000	292,000	210,000
Ending balance: individually evaluated for impairment	276,000				106,000				276,000	106,000	988,000
Ending balance: collectively evaluated for impairment	24,440,000				23,500,000				24,440,000	23,500,000	21,004,000
Unallocated Financing Receivables [Member]
Balance, beginning of year				111,000				437,000	111,000	437,000	101,000
Provision for Loan Losses									68,000		336,000
Losses charged off									0		0
Recoveries									0		0
Balance, end of year	179,000				111,000				179,000	111,000	437,000
Ending balance: individually evaluated for impairment
Ending balance: collectively evaluated for impairment	179,000								179,000		437,000
Ending balance: individually evaluated for impairment
Ending balance: collectively evaluated for impairment
Unallocated [Member]
Balance, beginning of year				$ 111,000				$ 437,000	$ 111,000	437,000
Provision for Loan Losses										(326,000)
Losses charged off										0
Recoveries										0
Balance, end of year					111,000					111,000	$ 437,000
Ending balance: individually evaluated for impairment					0					0
Ending balance: collectively evaluated for impairment					111,000					111,000
Ending balance: individually evaluated for impairment					0					0
Ending balance: collectively evaluated for impairment					$ 0					$ 0