Loans and allowance for loan losses (Details 9) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	$ 5,567	$ 5,844	$ 5,729	$ 5,681	$ 6,600	$ 7,239
Allowance Individually Evaluated for Impairment	1,112		1,512
Allowance Collectively Evaluated for Impairment	4,455		4,217
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	301,629		286,146
Loans Individually Evaluated for Impairment	30,638		32,280
Loans Collectively Evaluated for Impairment	270,991		253,866
Loans Acquired with Deteriorated Credit Quality	0		0
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	92	35	34	141	140	135
Allowance Individually Evaluated for Impairment	0		0
Allowance Collectively Evaluated for Impairment	35		34
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	5,967		4,315
Loans Individually Evaluated for Impairment	0		164
Loans Collectively Evaluated for Impairment	5,967		4,151
Loans Acquired with Deteriorated Credit Quality	0		0
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	369	88	202	770	849	1,274
Allowance Individually Evaluated for Impairment	25		26
Allowance Collectively Evaluated for Impairment	14		176
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	25,548		25,152
Loans Individually Evaluated for Impairment	3,293		3,968
Loans Collectively Evaluated for Impairment	22,255		21,184
Loans Acquired with Deteriorated Credit Quality	0		0
Home equity lines [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	441	$ 469	469	$ 225	$ 466	$ 424
Allowance Individually Evaluated for Impairment	0		0
Allowance Collectively Evaluated for Impairment	430		469
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	19,533		20,082
Loans Individually Evaluated for Impairment	1,468		800
Loans Collectively Evaluated for Impairment	18,065		19,282
Loans Acquired with Deteriorated Credit Quality	0		0
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	74		236
Allowance Individually Evaluated for Impairment	25		26
Allowance Collectively Evaluated for Impairment	49		210
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	31,515		29,467
Loans Individually Evaluated for Impairment	3,293		4,132
Loans Collectively Evaluated for Impairment	28,222		25,335
Loans Acquired with Deteriorated Credit Quality	0		0
Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	1,709		1,836
Allowance Individually Evaluated for Impairment	652		905
Allowance Collectively Evaluated for Impairment	1,057		931
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	63,715		58,804
Loans Individually Evaluated for Impairment	9,105		8,311
Loans Collectively Evaluated for Impairment	54,610		50,493
Loans Acquired with Deteriorated Credit Quality	0		0
Non-Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	609		607
Allowance Individually Evaluated for Impairment	38		0
Allowance Collectively Evaluated for Impairment	571		607
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	38,231		38,892
Loans Individually Evaluated for Impairment	6,586		6,593
Loans Collectively Evaluated for Impairment	31,645		32,299
Loans Acquired with Deteriorated Credit Quality	0		0
Multifamily [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	78		78
Allowance Individually Evaluated for Impairment	0		0
Allowance Collectively Evaluated for Impairment	78		78
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	8,989		11,438
Loans Individually Evaluated for Impairment	0		2,322
Loans Collectively Evaluated for Impairment	8,989		9,116
Loans Acquired with Deteriorated Credit Quality	0		0
Farmland [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	130		130
Allowance Individually Evaluated for Impairment	0		0
Allowance Collectively Evaluated for Impairment	130		130
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	400		434
Loans Individually Evaluated for Impairment	0		21
Loans Collectively Evaluated for Impairment	400		413
Loans Acquired with Deteriorated Credit Quality	0		0
First Deed of Trust [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	1,648		1,345
Allowance Individually Evaluated for Impairment	224		200
Allowance Collectively Evaluated for Impairment	1,424		1,145
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	59,965		61,837
Loans Individually Evaluated for Impairment	8,296		7,900
Loans Collectively Evaluated for Impairment	51,669		53,937
Loans Acquired with Deteriorated Credit Quality	0		0
Second Deed of Trust [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	233		275
Allowance Individually Evaluated for Impairment	153		142
Allowance Collectively Evaluated for Impairment	80		133
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	7,585		7,854
Loans Individually Evaluated for Impairment	1,319		1,360
Loans Collectively Evaluated for Impairment	6,266		6,494
Loans Acquired with Deteriorated Credit Quality	0		0
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	2,526		2,651
Allowance Individually Evaluated for Impairment	690		905
Allowance Collectively Evaluated for Impairment	1,836		1,746
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	111,335		109,568
Loans Individually Evaluated for Impairment	15,691		17,247
Loans Collectively Evaluated for Impairment	95,644		92,321
Loans Acquired with Deteriorated Credit Quality	0		0
Consumer Real Estate, Secured by 1-4 Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	2,311		2,089
Allowance Individually Evaluated for Impairment	377		342
Allowance Collectively Evaluated for Impairment	1,934		1,747
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	87,083		89,773
Loans Individually Evaluated for Impairment	11,083		10,060
Loans Collectively Evaluated for Impairment	76,000		79,713
Loans Acquired with Deteriorated Credit Quality	0		0
Commercial and industrial loans (except those secured by real estate) [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	402		506
Allowance Individually Evaluated for Impairment	20		239
Allowance Collectively Evaluated for Impairment	382		267
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	22,118		22,165
Loans Individually Evaluated for Impairment	541		818
Loans Collectively Evaluated for Impairment	21,577		21,347
Loans Acquired with Deteriorated Credit Quality	0		0
Guaranteed student loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	216		217
Allowance Individually Evaluated for Impairment	0		0
Allowance Collectively Evaluated for Impairment	216		217
Loans Ending Balance	48,051		33,562
Loans Individually Evaluated for Impairment	0		0
Loans Collectively Evaluated for Impairment	48,051		33,562
Loans Acquired with Deteriorated Credit Quality	0		0
Consumer And Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance Ending Balance	38		30
Allowance Individually Evaluated for Impairment	0		0
Allowance Collectively Evaluated for Impairment	38		30
Allowance Loans acquired with Deteriorated Credit Quality	0		0
Loans Ending Balance	1,527		1,611
Loans Individually Evaluated for Impairment	30		23
Loans Collectively Evaluated for Impairment	1,497		1,588
Loans Acquired with Deteriorated Credit Quality	$ 0		$ 0