Note 4 - Loans and Allowance for Loan Losses - Impaired Loans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Originated Loan [Member]
With no related allowance recorded, unpaid principal balance	$ 4,915,000	$ 3,499,000
With no related allowance recorded, principal balance	3,150,000	2,467,000
With no related allowance recorded, average recorded principal balance	2,580,000	6,583,000
With related allowance recorded, unpaid principal balance	5,837,000	11,008,000
With related allowance recorded, principal balance	5,637,000	10,916,000
Related allowance	1,867,000	1,572,000
With related allowance recorded, average recorded principal balance	8,954,000	8,869,000
Total unpaid principal balance	10,752,000	14,507,000
Total principal balance	8,787,000	13,383,000
Total average recorded principal balance	11,534,000	15,452,000
Originated Loan [Member] | Commercial Portfolio Segment [Member]
With no related allowance recorded, unpaid principal balance	3,096,000	2,115,000
With no related allowance recorded, principal balance	2,014,000	1,723,000
With no related allowance recorded, average recorded principal balance	1,458,000	5,671,000
With related allowance recorded, unpaid principal balance	4,447,000	10,370,000
With related allowance recorded, principal balance	4,380,000	10,347,000
Related allowance	1,202,000	1,303,000
With related allowance recorded, average recorded principal balance	7,910,000	8,276,000
Total unpaid principal balance	7,543,000	12,485,000
Total principal balance	6,394,000	12,070,000
Total average recorded principal balance	9,368,000	13,947,000
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
With no related allowance recorded, unpaid principal balance	765,000	1,498,000
With no related allowance recorded, principal balance	178,000	1,498,000
With no related allowance recorded, average recorded principal balance	694,000	1,574,000
With related allowance recorded, unpaid principal balance	3,038,000	2,405,000
With related allowance recorded, principal balance	2,989,000	2,382,000
Related allowance	963,000	673,000
With related allowance recorded, average recorded principal balance	3,314,000	717,000
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
With no related allowance recorded, unpaid principal balance	454,000	487,000
With no related allowance recorded, principal balance	35,000	95,000
With no related allowance recorded, average recorded principal balance	65,000	32,000
With related allowance recorded, unpaid principal balance	0	999,000
With related allowance recorded, principal balance	0	999,000
Related allowance	0	28,000
With related allowance recorded, average recorded principal balance	449,000	1,011,000
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
With no related allowance recorded, unpaid principal balance	1,528,000	0
With no related allowance recorded, principal balance	1,452,000	0
With no related allowance recorded, average recorded principal balance	442,000	270,000
With related allowance recorded, unpaid principal balance	1,409,000	906,000
With related allowance recorded, principal balance	1,391,000	906,000
Related allowance	239,000	97,000
With related allowance recorded, average recorded principal balance	1,663,000	2,095,000
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
With no related allowance recorded, unpaid principal balance	0	0
With no related allowance recorded, principal balance	0	0
With no related allowance recorded, average recorded principal balance	36,000	3,752,000
With related allowance recorded, unpaid principal balance	0	5,020,000
With related allowance recorded, principal balance	0	5,020,000
Related allowance	0	247,000
With related allowance recorded, average recorded principal balance	2,055,000	3,641,000
Originated Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
With no related allowance recorded, unpaid principal balance	349,000	130,000
With no related allowance recorded, principal balance	349,000	130,000
With no related allowance recorded, average recorded principal balance	221,000	43,000
With related allowance recorded, unpaid principal balance	0	1,040,000
With related allowance recorded, principal balance	0	1,040,000
Related allowance	0	258,000
With related allowance recorded, average recorded principal balance	429,000	812,000
Originated Loan [Member] | Retail Portfolio Segment [Member]
With no related allowance recorded, unpaid principal balance	1,819,000	1,384,000
With no related allowance recorded, principal balance	1,136,000	744,000
With no related allowance recorded, average recorded principal balance	1,122,000	912,000
With related allowance recorded, unpaid principal balance	1,390,000	638,000
With related allowance recorded, principal balance	1,257,000	569,000
Related allowance	665,000	269,000
With related allowance recorded, average recorded principal balance	1,044,000	593,000
Total unpaid principal balance	3,209,000	2,022,000
Total principal balance	2,393,000	1,313,000
Total average recorded principal balance	2,166,000	1,505,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
With no related allowance recorded, unpaid principal balance	693,000	114,000
With no related allowance recorded, principal balance	680,000	114,000
With no related allowance recorded, average recorded principal balance	526,000	99,000
With related allowance recorded, unpaid principal balance	1,225,000	434,000
With related allowance recorded, principal balance	1,147,000	412,000
Related allowance	652,000	203,000
With related allowance recorded, average recorded principal balance	922,000	449,000
Originated Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
With no related allowance recorded, unpaid principal balance	1,126,000	1,270,000
With no related allowance recorded, principal balance	456,000	630,000
With no related allowance recorded, average recorded principal balance	596,000	813,000
With related allowance recorded, unpaid principal balance	165,000	204,000
With related allowance recorded, principal balance	110,000	157,000
Related allowance	13,000	66,000
With related allowance recorded, average recorded principal balance	122,000	144,000
Acquired Loan [Member]
With no related allowance recorded, unpaid principal balance	5,938,000	5,826,000
With no related allowance recorded, principal balance	4,795,000	4,894,000
With no related allowance recorded, average recorded principal balance	5,504,000	5,405,000
With related allowance recorded, unpaid principal balance	0	239,000
With related allowance recorded, principal balance	0	239,000
Related allowance	0	9,000
With related allowance recorded, average recorded principal balance	185,000	370,000
Total unpaid principal balance	5,938,000	6,065,000
Total principal balance	4,795,000	5,133,000
Total average recorded principal balance	5,689,000	5,775,000
Acquired Loan [Member] | Commercial Portfolio Segment [Member]
With no related allowance recorded, unpaid principal balance	2,541,000	3,214,000
With no related allowance recorded, principal balance	2,135,000	2,914,000
With no related allowance recorded, average recorded principal balance	3,202,000	3,454,000
With related allowance recorded, unpaid principal balance	0	67,000
With related allowance recorded, principal balance	0	67,000
Related allowance	0	5,000
With related allowance recorded, average recorded principal balance	48,000	250,000
Total unpaid principal balance	2,541,000	3,281,000
Total principal balance	2,135,000	2,981,000
Total average recorded principal balance	3,250,000	3,704,000
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
With no related allowance recorded, unpaid principal balance	1,039,000	853,000
With no related allowance recorded, principal balance	1,021,000	826,000
With no related allowance recorded, average recorded principal balance	1,039,000	1,074,000
With related allowance recorded, unpaid principal balance	0	19,000
With related allowance recorded, principal balance	0	19,000
Related allowance	0	2,000
With related allowance recorded, average recorded principal balance	10,000	207,000
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Vacant Land and Land Development and Residential Construction Loan [Member]
With no related allowance recorded, unpaid principal balance	0	0
With no related allowance recorded, principal balance	0	0
With no related allowance recorded, average recorded principal balance	12,000	0
With related allowance recorded, unpaid principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	0	0
With related allowance recorded, average recorded principal balance	0	0
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Owner Occupied Loan [Member]
With no related allowance recorded, unpaid principal balance	1,027,000	1,281,000
With no related allowance recorded, principal balance	659,000	1,210,000
With no related allowance recorded, average recorded principal balance	1,005,000	1,145,000
With related allowance recorded, unpaid principal balance	0	48,000
With related allowance recorded, principal balance	0	48,000
Related allowance	0	3,000
With related allowance recorded, average recorded principal balance	38,000	38,000
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Non Owner Occupied Loan [Member]
With no related allowance recorded, unpaid principal balance	238,000	928,000
With no related allowance recorded, principal balance	237,000	789,000
With no related allowance recorded, average recorded principal balance	738,000	932,000
With related allowance recorded, unpaid principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	0	0
With related allowance recorded, average recorded principal balance	0	0
Acquired Loan [Member] | Commercial Portfolio Segment [Member] | Real Estate Multi Family and Residential Rental Loan [Member]
With no related allowance recorded, unpaid principal balance	237,000	152,000
With no related allowance recorded, principal balance	218,000	89,000
With no related allowance recorded, average recorded principal balance	408,000	303,000
With related allowance recorded, unpaid principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	0	0
With related allowance recorded, average recorded principal balance	0	5,000
Acquired Loan [Member] | Retail Portfolio Segment [Member]
With no related allowance recorded, unpaid principal balance	3,397,000	2,612,000
With no related allowance recorded, principal balance	2,660,000	1,980,000
With no related allowance recorded, average recorded principal balance	2,302,000	1,951,000
With related allowance recorded, unpaid principal balance	0	172,000
With related allowance recorded, principal balance	0	172,000
Related allowance	0	4,000
With related allowance recorded, average recorded principal balance	137,000	120,000
Total unpaid principal balance	3,397,000	2,784,000
Total principal balance	2,660,000	2,152,000
Total average recorded principal balance	2,439,000	2,071,000
Acquired Loan [Member] | Retail Portfolio Segment [Member] | Home Equity and Other [Member]
With no related allowance recorded, unpaid principal balance	694,000	531,000
With no related allowance recorded, principal balance	507,000	351,000
With no related allowance recorded, average recorded principal balance	417,000	389,000
With related allowance recorded, unpaid principal balance	0	0
With related allowance recorded, principal balance	0	0
Related allowance	0	0
With related allowance recorded, average recorded principal balance	0	0
Acquired Loan [Member] | Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
With no related allowance recorded, unpaid principal balance	2,703,000	2,081,000
With no related allowance recorded, principal balance	2,153,000	1,629,000
With no related allowance recorded, average recorded principal balance	1,885,000	1,562,000
With related allowance recorded, unpaid principal balance	0	172,000
With related allowance recorded, principal balance	0	172,000
Related allowance	0	4,000
With related allowance recorded, average recorded principal balance	$ 137,000	$ 120,000