Loans and reserve for credit losses (Details 8) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Number of loans	1	26	9	54
TDR outstanding recorded investment	$ 3	$ 5,031	$ 27,954	$ 7,355
Commerical real estate [Member]
Number of loans	0	1	5	4
TDR outstanding recorded investment	0	132	27,677	1,729
Construction [Member]
Number of loans	0	1	0	1
TDR outstanding recorded investment	0	4,425	0	4,425
Residential real estate [Member]
Number of loans	0	3	0	7
TDR outstanding recorded investment	0	83	0	310
Commercial and industrial loans [Member]
Number of loans	1	3	4	9
TDR outstanding recorded investment	3	240	277	581
Consumer Loans [Member]
Number of loans	0	18	0	33
TDR outstanding recorded investment	$ 0	$ 151	$ 0	$ 310