Loans and allowance for loan losses (Details 8) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 5,844	$ 6,600	$ 5,729	$ 7,239	$ 7,239
Provision for Loan and Lease Losses	0	0	0	100	100
Charge-offs	(363)	(1,157)	(642)	(1,953)	(2,381)
Recoveries	86	238	480	295	771
Ending balance	5,567	5,681	5,567	5,681	5,729
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	35	140	34	135	135
Provision for Loan and Lease Losses	57	0	57	5	(103)
Charge-offs	0	0	0	0	0
Recoveries	0	1	1	1	2
Ending balance	92	141	92	141	34
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	88	849	202	1,274	1,274
Provision for Loan and Lease Losses	331	0	330	(421)	(1,016)
Charge-offs	(71)	(79)	(185)	(100)	(100)
Recoveries	21	0	22	17	44
Ending balance	369	770	369	770	202
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,651	2,279	2,651	2,226	2,226
Provision for Loan and Lease Losses	36	0	36	349	1,645
Charge-offs	(127)	(645)	(127)	(942)	(1,245)
Recoveries	2	23	2	23	25
Ending balance	2,562	1,656	2,562	1,656	2,651
Home equity lines [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	469	466	469	424	424
Provision for Loan and Lease Losses	11	0	11	223	506
Charge-offs	(40)	(243)	(40)	(424)	(476)
Recoveries	1	2	1	2	15
Ending balance	441	225	441	225	469
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	123	989	236	1,409	1,409
Provision for Loan and Lease Losses	388	0	387	(416)	(1,119)
Charge-offs	(71)	(79)	(185)	(100)	(100)
Recoveries	21	1	23	18	46
Ending balance	461	911	461	911	236
Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,836	1,853	1,836	1,199	1,199
Provision for Loan and Lease Losses	(23)	0	(23)	653	1,268
Charge-offs	(127)	(607)	(127)	(608)	(631)
Recoveries	0	0	0	0	0
Ending balance	1,686	1,244	1,686	1,244	1,836
Non-Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	607	0	607	670	670
Provision for Loan and Lease Losses	30	0	30	(470)	430
Charge-offs	0	(38)	0	(238)	(518)
Recoveries	2	23	2	23	25
Ending balance	639	(15)	639	(15)	607
Multifamily [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	78	17	78	20	20
Provision for Loan and Lease Losses	32	0	32	(2)	58
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Ending balance	110	18	110	18	78
Farmland [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	130	409	130	337	337
Provision for Loan and Lease Losses	(3)	0	(3)	168	(111)
Charge-offs	0	0	0	(96)	(96)
Recoveries	0	0	0	0	0
Ending balance	127	409	127	409	130
First Deed of Trust [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,703	1,755	1,345	1,992	1,992
Provision for Loan and Lease Losses	(456)	0	(456)	(65)	(442)
Charge-offs	(66)	(53)	(66)	(238)	(277)
Recoveries	11	42	369	55	72
Ending balance	1,192	1,744	1,192	1,744	1,345
Second Deed of Trust [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	284	329	275	394	394
Provision for Loan and Lease Losses	17	0	17	12	(223)
Charge-offs	(55)	1	(55)	(76)	(86)
Recoveries	4	110	13	110	190
Ending balance	250	440	250	440	275
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,456	2,550	2,089	2,810	2,810
Provision for Loan and Lease Losses	(428)	0	(428)	170	(159)
Charge-offs	(161)	(295)	(161)	(738)	(839)
Recoveries	16	154	383	167	277
Ending balance	1,883	2,409	1,883	2,409	2,089
Commercial and industrial loans (except those secured by real estate) [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	356	760	506	724	724
Provision for Loan and Lease Losses	(20)	0	(20)	45	(447)
Charge-offs	0	(136)	(162)	(168)	(172)
Recoveries	46	53	58	77	401
Ending balance	382	678	382	678	506
Guaranteed student loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	217		217	0	0
Provision for Loan and Lease Losses	37		37		217
Charge-offs	(1)		(1)		0
Recoveries	0		0		0
Ending balance	253		253		217
Consumer And Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	41	22	30	70	70
Provision for Loan and Lease Losses	(13)	0	(12)	(48)	(37)
Charge-offs	(3)	(2)	(6)	(5)	(25)
Recoveries	1	7	14	10	22
Ending balance	$ 26	$ 27	$ 26	$ 27	$ 30