Loans and reserve for credit losses (Details 9) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Rate reduction	$ 0	$ 0	$ 3,983	$ 1,384
Term extension	3	5,031	2,471	5,818
Rate reduction and term extension	0	0	21,500	153
Total	3	5,031	27,954	7,355
Commerical real estate [Member]
Rate reduction	0	0	3,809	1,295
Term extension	0	132	2,368	434
Rate reduction and term extension	0	0	21,500	0
Total	0	132	27,677	1,729
Construction [Member]
Rate reduction	0	0	0	0
Term extension	0	4,425	0	4,425
Rate reduction and term extension	0	0	0	0
Total	0	4,425	0	4,425
Residential real estate [Member]
Rate reduction	0	0	0	0
Term extension	0	83	0	310
Rate reduction and term extension	0	0	0	0
Total	0	83	0	310
Commercial and industrial loans [Member]
Rate reduction	0	0	174	89
Term extension	3	240	103	339
Rate reduction and term extension	0	0	0	153
Total	3	240	277	581
Consumer Loans [Member]
Rate reduction	0	0	0	0
Term extension	0	151	0	310
Rate reduction and term extension	0	0	0	0
Total	$ 0	$ 151	$ 0	$ 310