Derivatives (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) contracts	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) contracts	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Credit Derivatives [Line Items]
Counterparty default losses on forward contracts	$ 0	$ 0	$ 0	$ 0
Commitments and contingent liabilities
Number of interest rate derivatives held | contracts	440		440
Termination value of derivatives in net liability position	$ 87,500,000		$ 87,500,000		40,200,000
Collateral posting clearing	111,000,000		111,000,000		$ 58,700,000
Decrease in settlement values of the Bank's derivative assets	5,000,000		5,000,000
Interest Rate Swap
Credit Derivatives [Line Items]
Notional amount of credit risk derivatives	2,100,000,000		2,100,000,000
Commitments To Originate Loans Held For Sale
Credit Derivatives [Line Items]
Commitments and contingent liabilities	594,978,000		594,978,000
Interest Rate Forward Sales Commitments
Credit Derivatives [Line Items]
Commitments and contingent liabilities	$ 796,323,000		$ 796,323,000