Derivative Instruments and Hedging Activities - Notional Amounts and Fair Values of Derivatives not Designated as Hedging Instruments (Details) (Not designated as hedging instruments [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Notional amounts and fair values of derivatives not designated as hedging instruments
Notional Amount	$ 133,619	$ 75,014
Derivative Assets, Fair Value	2,026	1,079
Derivative Liabilities, Fair Value	412	302
Interest rate locks with customers [Member]
Notional amounts and fair values of derivatives not designated as hedging instruments
Notional Amount	66,147	35,934
Forward loan commitments [Member]
Notional amounts and fair values of derivatives not designated as hedging instruments
Notional Amount	67,472	39,080
Other Assets [Member] | Interest rate locks with customers [Member]
Notional amounts and fair values of derivatives not designated as hedging instruments
Derivative Assets, Fair Value	2,026	1,079
Other Liabilities [Member] | Forward loan commitments [Member]
Notional amounts and fair values of derivatives not designated as hedging instruments
Derivative Liabilities, Fair Value	$ 412	$ 302