Derivative Instruments (Narrative) (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified within 12 months	$ (383,000)
Remaining unamortized deferred gain (loss) balance of all previously terminated cash flow hedges	(2,200,000)		(630,000)
Remaining deferred gain (loss) balance on all previously terminated fair value hedges	16,000,000		21,200,000
Unrealized loss on mortgage loans derivative	2,100,000		446,000
Collateral pledge to collateralize derivative liabilities	113,600,000
Fixed Rate Residential Mortgage [Member]
Derivative [Line Items]
Commitments to fund fixed-rate mortgage loans	220,900,000		115,500,000
Unrealized gain on fair value of fixed-rate mortgage loans to customers	3,900,000	1,200,000
Sale of outstanding commitments	284,500,000		202,500,000
Interest Rate Swap [Member] | Customer Related Interest Rate Risk [Member]
Derivative [Line Items]
Notional amount of interest rate swap contracts	$ 1,200,000,000		$ 280,600,000