Loans and reserve for credit losses (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Increase (Decrease) in Finance Receivables	$ 11,100,000
Percentage Of Real Estate Related Loans	69.50%
Loans participated to third-parties	11,300,000		11,300,000
Reductions in Loans Classified as Special Mention and Substandard	17,800,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	90,000		1,083,000
Impaired loans,Total recorded balance	36,524,000		40,467,000
Loans and Leases Receivable, Allowance	21,722,000		20,857,000
Troubled Debt Restructuring
Financing Receivable, Impaired [Line Items]
Impaired loans,Total recorded balance	31,100,000		33,200,000
Loans and Leases Receivable, Allowance	1,000,000		800,000
Remaining Commitment To Lend Loan	0	20,000
Unallocated Financing Receivables
Financing Receivable, Impaired [Line Items]
Provision for Loan and Lease Losses	1,300,000
Loans and Leases Receivable, Allowance	2,007,000		714,000
Loans Receivable
Financing Receivable, Impaired [Line Items]
Provision for Loan and Lease Losses	0	0
Loans and Leases Receivable, Allowance	21,722,000	24,548,000	20,857,000	27,261,000
Loans Receivable | Unallocated Financing Receivables
Financing Receivable, Impaired [Line Items]
Provision for Loan and Lease Losses	1,293,000	(429,000)
Loans and Leases Receivable, Allowance	$ 2,007,000	$ 658,000	$ 714,000	$ 1,087,000