Derivative Financial instruments (Net Impact on Interest Expense Related to Fair Value Hedges) (Details) (Fair Value Hedging [Member], Designated as Hedging Instrument [Member], Interest Expense [Member], USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Net impact on other non-interest income	$ (3,404,000)	$ (5,845,000)	$ (7,847,000)
Interest Rate Swap [Member] | Senior Notes [Member]
Derivative [Line Items]
Net impact on other non-interest income	(3,197,000)	(3,197,000)	(3,197,000)
Interest Rate Swap [Member] | Subordinated Debt [Member]
Derivative [Line Items]
Net impact on other non-interest income	(207,000)	(2,648,000)	(4,479,000)
Interest Rate Swap [Member] | Federal Home Loan Bank Advances [Member]
Derivative [Line Items]
Net impact on other non-interest income	$ 0	$ 0	$ (171,000)