Derivatives (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Credit Derivatives [Line Items]
Counterparty default losses on forward contracts	$ 0	$ 0
Commitments to originate loans held for sale	171,900,000
Commitments and contingent liabilities
Notional amount of credit risk derivatives	364,400,000
Number of interest rate derivatives held	78
Termination value of derivatives in net liability position	7,300,000
Minimum collateral posting agreement amount	6,900,000
Increase in Bank's derivative asset due to net credit valuation adjustment	379,000
Gain on nonhedge derivative instruments related to credit valuation adjustments	584,000
Interest Rate Forward Sales Commitments [Member]
Credit Derivatives [Line Items]
Commitments and contingent liabilities	$ 220,628,000