Derivatives (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) contracts	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) contracts
Credit Derivatives [Line Items]
Counterparty default losses on forward contracts	$ 0	$ 0
Number of interest rate derivatives held | contracts	548		516
Termination value of derivatives in net liability position	$ 6,300,000		$ 34,900,000
Collateral posting clearing	27,100,000		50,300,000
Variation Margin Payment	21,900,000
Decrease in settlement values of the Bank's derivative assets	945,000		241,000
Interest Rate Swap
Credit Derivatives [Line Items]
Notional amount of credit risk derivatives	2,500,000,000		$ 2,300,000,000
Commitments To Originate Loans Held For Sale
Credit Derivatives [Line Items]
Commitments and contingent liabilities	447,676,000
Interest Rate Forward Sales Commitments
Credit Derivatives [Line Items]
Commitments and contingent liabilities	$ 626,430,000