Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Interest rate swap contracts [Member] | Derivatives Designated as Cash Flow Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative asset notional amount	$ 33.0	$ 33.0
Pledged collateral to derivative counterparties	1.8	1.9
Interest rate swaps with customers [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative asset notional amount	61.0	61.6
Mirror swaps with counterparties [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative asset notional amount	$ 61.0	$ 61.6