Loans and allowance for credit losses (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2014 Impaired Nonaccrual Loans [Member]	Jun. 30, 2013 Impaired Nonaccrual Loans [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Construction Loans [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Construction Loans [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Construction Loans [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Construction Loans [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Residential Real Estate [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Residential Real Estate [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Residential Real Estate [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Residential Real Estate [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Commercial Real Estate [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Commercial Real Estate [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Commercial Loan [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Commercial Loan [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Commercial Loan [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Commercial Loan [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Consumer Loan [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Consumer Loan [Member]	Jun. 30, 2014 Impaired Nonaccrual Loans [Member] Consumer Loan [Member]	Dec. 31, 2013 Impaired Nonaccrual Loans [Member] Consumer Loan [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Construction Loans [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Construction Loans [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Construction Loans [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Construction Loans [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Residential Real Estate [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Residential Real Estate [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Residential Real Estate [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Residential Real Estate [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Commercial Real Estate [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Commercial Real Estate [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Commercial Loan [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Commercial Loan [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Commercial Loan [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Commercial Loan [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Consumer Loan [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Consumer Loan [Member]	Jun. 30, 2014 Impaired Accruing TDRs [Member] Consumer Loan [Member]	Dec. 31, 2013 Impaired Accruing TDRs [Member] Consumer Loan [Member]	Jun. 30, 2014 Total Impired Loans [Member]	Dec. 31, 2013 Total Impired Loans [Member]	Jun. 30, 2014 Total Impired Loans [Member]	Dec. 31, 2013 Total Impired Loans [Member]	Jun. 30, 2014 Total Impired Loans [Member] Construction Loans [Member]	Dec. 31, 2013 Total Impired Loans [Member] Construction Loans [Member]	Jun. 30, 2014 Total Impired Loans [Member] Construction Loans [Member]	Dec. 31, 2013 Total Impired Loans [Member] Construction Loans [Member]	Jun. 30, 2014 Total Impired Loans [Member] Residential Real Estate [Member]	Dec. 31, 2013 Total Impired Loans [Member] Residential Real Estate [Member]	Jun. 30, 2014 Total Impired Loans [Member] Residential Real Estate [Member]	Dec. 31, 2013 Total Impired Loans [Member] Residential Real Estate [Member]	Jun. 30, 2014 Total Impired Loans [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Total Impired Loans [Member] Commercial Real Estate [Member]	Jun. 30, 2014 Total Impired Loans [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Total Impired Loans [Member] Commercial Real Estate [Member]	Jun. 30, 2014 Total Impired Loans [Member] Commercial Loan [Member]	Dec. 31, 2013 Total Impired Loans [Member] Commercial Loan [Member]	Jun. 30, 2014 Total Impired Loans [Member] Commercial Loan [Member]	Dec. 31, 2013 Total Impired Loans [Member] Commercial Loan [Member]	Jun. 30, 2014 Total Impired Loans [Member] Consumer Loan [Member]	Dec. 31, 2013 Total Impired Loans [Member] Consumer Loan [Member]	Jun. 30, 2014 Total Impired Loans [Member] Consumer Loan [Member]	Dec. 31, 2013 Total Impired Loans [Member] Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 22,481		$ 22,481	$ 21,554	$ 12,263	$ 6,787	$ 12,263	$ 6,787	$ 3,915	$ 7,692	$ 3,915	$ 7,692	$ 5,801	$ 5,218	$ 5,801	$ 5,218	$ 472	$ 1,801	$ 472	$ 1,801	$ 30	$ 56	$ 30	$ 56	$ 25,402	$ 26,088	$ 25,402	$ 26,088	$ 3,898	$ 1,620	$ 3,898	$ 1,620	$ 16,195	$ 14,582	$ 16,195	$ 14,582	$ 5,253	$ 9,791	$ 5,253	$ 9,791	$ 56	$ 95	$ 56	$ 95	$ 0	$ 0	$ 0	$ 0	$ 47,883	$ 47,642	$ 47,883	$ 47,642	$ 16,161	$ 8,407	$ 16,161	$ 8,407	$ 20,110	$ 22,274	$ 20,110	$ 22,274	$ 11,054	$ 15,009	$ 11,054	$ 15,009	$ 528	$ 1,896	$ 528	$ 1,896	$ 30	$ 56	$ 30	$ 56
Recorded investment with no allowance	13,683		13,683	12,422	7,780	3,709	7,780	3,709	2,780	3,862	2,780	3,862	2,927	4,261	2,927	4,261	196	547	196	547	0	43	0	43	21,106	23,805	21,106	23,805	3,809	1,527	3,809	1,527	12,761	13,177	12,761	13,177	4,480	9,006	4,480	9,006	56	95	56	95	0	0	0	0	34,789	36,227	34,789	36,227	11,589	5,236	11,589	5,236	15,541	17,039	15,541	17,039	7,407	13,267	7,407	13,267	252	642	252	642	0	43	0	43
Recorded investment with an allowance	1,493		1,493	2,204	200	240	200	240	257	1,304	257	1,304	946	410	946	410	65	245	65	245	25	5	25	5	4,296	2,283	4,296	2,283	89	93	89	93	3,434	1,405	3,434	1,405	773	785	773	785	0	0	0	0	0	0	0	0	5,789	4,487	5,789	4,487	289	333	289	333	3,691	2,709	3,691	2,709	1,719	1,195	1,719	1,195	65	245	65	245	25	5	25	5
Related allowance	433		433	716	200	203	200	203	125	225	125	225	18	38	18	38	65	245	65	245	25	5	25	5	192	67	192	67	1	1	1	1	185	60	185	60	6	6	6	6	0	0	0	0	0	0	0	0	625	783	625	783	201	204	201	204	310	285	310	285	24	44	24	44	65	245	65	245	25	5	25	5
Average recorded investment	$ 16,999	$ 15,363	$ 18,611	$ 26,006	$ 8,040	$ 5,563	$ 8,131	$ 7,270	$ 3,299	$ 5,094	$ 4,719	$ 10,240	$ 5,034	$ 3,917	$ 5,098	$ 7,829	$ 598	$ 740	$ 642	$ 619	$ 28	$ 49	$ 21	$ 48	$ 25,319	$ 27,445	$ 25,426	$ 38,919	$ 2,157	$ 1,759	$ 1,749	$ 14,405	$ 16,080	$ 15,387	$ 16,102	$ 11,101	$ 7,023	$ 10,201	$ 7,509	$ 13,308	$ 59	$ 98	$ 66	$ 105	$ 0	$ 0	$ 0	$ 0	$ 42,318	$ 42,808	$ 44,037	$ 64,925	$ 10,197	$ 7,322	$ 9,880	$ 21,675	$ 19,379	$ 20,481	$ 20,821	$ 21,341	$ 12,057	$ 14,118	$ 12,607	$ 21,137	$ 657	$ 838	$ 708	$ 724	$ 28	$ 49	$ 21	$ 48