Derivative Instruments (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified within 12 months	$ (447)
Remaining unamortized deferred gain (loss) balance of all previously terminated cash flow hedges	(782)		$ (1,100)
Remaining deferred gain (loss) balance on all previously terminated fair value hedges	5,300		7,600
Deferred gain balance on terminated fair value hedges expected to be reclassified from long-term debt	3,100
Derivative, fair value	1,400
Gain (loss) on sale of outstanding commitments	(356)	$ (1,200)
Deferred gains (loss) on discontinuation of cash flow hedge reclassified to earnings	2,300	1,500
Fixed Rate Residential Mortgage [Member]
Derivative [Line Items]
Commitments to fund fixed-rate mortgage loans	93,200		73,400
Unrealized gain on fair value of fixed-rate mortgage loans to customers	632	$ 531
Sale of outstanding commitments	111,500		113,000
Interest Rate Swap [Member] | Customer Related Interest Rate Risk [Member]
Derivative [Line Items]
Notional amount of interest rate swap contracts	1,190,000		$ 103,700
Federal Funds Sold [Member]
Derivative [Line Items]
Federal funds sold	68,400
Federal Funds Sold, Counterparty with CCC [Member]
Derivative [Line Items]
Federal funds sold	$ 12,600