Derivatives (Narrative) (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) contracts	Dec. 31, 2014 USD ($) contracts	Dec. 31, 2013 USD ($)
Credit Derivatives [Line Items]
Counterparty default losses on forward contracts	$ 0	$ 0	$ 0
Commitments and contingent liabilities
Number of interest rate derivatives held | contracts	381	302
Notional amount of credit risk derivatives	$ 1,900,000,000	$ 1,400,000,000
Termination value of derivatives in net liability position	40,200,000	29,000,000
Required collateral posting	58,700,000	43,500,000
Increase (decrease) in settlement values of the Bank's derivative assets	1,900,000	$ 1,900,000
Commitments To Originate Loans Held For Sale [Member]
Credit Derivatives [Line Items]
Commitments and contingent liabilities	341,263,000
Interest Rate Forward Sales Commitments [Member]
Credit Derivatives [Line Items]
Commitments and contingent liabilities	$ 556,568,000