Benefit plans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Benefit Plans [Line Items]
Contributions to 401(k) profit sharing plan	$ 500,000	$ 500,000	$ 200,000
Bank Owned Life Insurance	36,567,000	35,705,000
Deferred Compensation, Excluding Share-based Payments and Retirement Benefits
Benefit Plans [Line Items]
Other Postretirement Defined Benefit Plan, Liabilities	3,900,000	4,000,000
Deferred Compensation Arrangement with Individual, Compensation Expense	100,000	200,000	400,000
Supplemental Employee Retirement Plans, Defined Benefit
Benefit Plans [Line Items]
Other Postretirement Defined Benefit Plan, Liabilities	12,700,000	12,500,000
Deferred Compensation Arrangement with Individual, Compensation Expense	800,000	(500,000)	3,800,000
General Account BOLI
Benefit Plans [Line Items]
Bank Owned Life Insurance	8,700,000	8,400,000
Separate Account BOLI
Benefit Plans [Line Items]
Bank Owned Life Insurance	$ 27,900,000	$ 27,300,000