Note 3 - Impaired Loan Data (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Unpaid contractual principal balance with no related allowance	$ 502	$ 492	$ 454
Impaired balance with no related allowance	500	464	454
Average recorded investment with no related allowance	477	386	535
Interest income recognized with no related allowance	2	(7)	17
Interest income collected with no related allowance	3	5	21
Unpaid contractual principal balance with an allowance	29	94	123
Impaired balance with an allowance	28	94	123
Related allowance	4	94	95
Average recorded investment with an allowance	76	95	100
Interest income recognized with an allowance			2
Interest income collected with an allowance			3
Unpaid contractual principal balance	531	586	577
Impaired balance	528	558	577
Average recorded investment	553	481	635
Interest income recognized	2	(7)	19
Interest income collected	3	5	24
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Unpaid contractual principal balance with no related allowance	213	174	196
Impaired balance with no related allowance	193	156	178
Average recorded investment with no related allowance	185	101	163
Interest income recognized with no related allowance	7	(10)	(10)
Interest income collected with no related allowance	10	10	10
Unpaid contractual principal balance	213	174	196
Impaired balance	193	156	178
Average recorded investment	185	101	163
Interest income recognized	7	(10)	(10)
Interest income collected	10	10	10
Real Estate Portfolio Segment [Member] | Commercial [Member]
Unpaid contractual principal balance with no related allowance	10,439	17,531	15,569
Impaired balance with no related allowance	9,992	17,037	15,122
Average recorded investment with no related allowance	12,557	16,632	15,430
Interest income recognized with no related allowance	89	157	529
Interest income collected with no related allowance	93	163	531
Unpaid contractual principal balance with an allowance	7,279	5,463	8,969
Impaired balance with an allowance	7,265	5,463	8,956
Related allowance	1,940	209	1,608
Average recorded investment with an allowance	8,110	5,799	6,673
Interest income recognized with an allowance	50	45	214
Interest income collected with an allowance	52	45	209
Unpaid contractual principal balance	17,718	22,994	24,538
Impaired balance	17,257	22,500	24,078
Average recorded investment	20,667	22,431	22,103
Interest income recognized	139	202	743
Interest income collected	145	208	740
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Unpaid contractual principal balance with no related allowance	466	9,537	6,888
Impaired balance with no related allowance	466	3,428	1,897
Average recorded investment with no related allowance	1,182	3,446	2,867
Interest income recognized with no related allowance	4	6	26
Interest income collected with no related allowance	3	7	27
Unpaid contractual principal balance with an allowance	75	206	77
Impaired balance with an allowance	75	134	77
Related allowance	24	49	25
Average recorded investment with an allowance	76	136	92
Unpaid contractual principal balance	541	9,743	6,965
Impaired balance	541	3,562	1,974
Average recorded investment	1,258	3,582	2,959
Interest income recognized	4	6	26
Interest income collected	3	7	27
Real Estate Portfolio Segment [Member] | Residential [Member]
Unpaid contractual principal balance with no related allowance	5,209	6,141	5,429
Impaired balance with no related allowance	4,288	5,195	4,576
Average recorded investment with no related allowance	4,432	6,397	4,715
Interest income recognized with no related allowance	52	42	176
Interest income collected with no related allowance	48	47	159
Unpaid contractual principal balance with an allowance	971	1,209	1,083
Impaired balance with an allowance	964	1,103	1,075
Related allowance	528	330	308
Average recorded investment with an allowance	1,019	1,584	1,089
Interest income recognized with an allowance	1	13	16
Interest income collected with an allowance	1	6	16
Unpaid contractual principal balance	6,180	7,350	6,512
Impaired balance	5,252	6,298	5,651
Average recorded investment	5,451	7,981	5,804
Interest income recognized	53	55	192
Interest income collected	49	53	175
Real Estate Portfolio Segment [Member] | Farmland [Member]
Unpaid contractual principal balance with no related allowance	1,328	1,419	1,105
Impaired balance with no related allowance	1,327	1,417	1,103
Average recorded investment with no related allowance	1,215	1,433	1,340
Interest income recognized with no related allowance	(4)	3	1
Interest income collected with no related allowance		3	2
Unpaid contractual principal balance with an allowance	386	394	388
Impaired balance with an allowance	386	394	388
Related allowance	35	53	37
Average recorded investment with an allowance	387	395	391
Interest income recognized with an allowance	5	5	21
Interest income collected with an allowance	5	5	21
Unpaid contractual principal balance	1,714	1,813	1,493
Impaired balance	1,713	1,811	1,491
Average recorded investment	1,602	1,828	1,731
Interest income recognized	1	8	22
Interest income collected	5	8	23
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Unpaid contractual principal balance with no related allowance	207	200	180
Impaired balance with no related allowance	195	192	178
Average recorded investment with no related allowance	187	197	191
Interest income recognized with no related allowance	1	1	14
Interest income collected with no related allowance	4	4	15
Unpaid contractual principal balance	207	200	180
Impaired balance	195	192	178
Average recorded investment	187	197	191
Interest income recognized	1	1	14
Interest income collected	4	4	$ 15
Consumer and Other Portfolio Segment [Member] | Other [Member]
Unpaid contractual principal balance with no related allowance		205
Impaired balance with no related allowance		194
Average recorded investment with no related allowance		195	$ 48
Interest income recognized with no related allowance		2
Interest income collected with no related allowance		2
Unpaid contractual principal balance		205
Impaired balance		194
Average recorded investment		195	$ 48
Interest income recognized		2
Interest income collected		2
Unpaid contractual principal balance with no related allowance	18,364	35,699	29,821
Impaired balance with no related allowance	16,961	28,083	23,508
Average recorded investment with no related allowance	20,235	28,787	25,289
Interest income recognized with no related allowance	151	194	753
Interest income collected with no related allowance	161	241	765
Unpaid contractual principal balance with an allowance	8,740	7,366	10,640
Impaired balance with an allowance	8,718	7,188	10,619
Related allowance	2,531	735	2,073
Average recorded investment with an allowance	9,668	8,009	8,345
Interest income recognized with an allowance	56	63	253
Interest income collected with an allowance	58	56	249
Unpaid contractual principal balance	27,104	43,065	40,461
Impaired balance	25,679	35,271	34,127
Average recorded investment	29,903	36,796	33,634
Interest income recognized	207	257	1,006
Interest income collected	$ 219	$ 297	$ 1,014