Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
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	2.0	2.0
Interest rate swaps with customers [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative asset notional amount	63.9	70.5
Mirror swaps with counterparties [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative asset notional amount	$ 63.9	$ 70.5