Derivative Instruments and Hedging Activities - Notional Amounts and Fair Values for Derivatives Designated as Hedging Instruments (Details 1) (Designated as hedging instruments [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Notional amounts and fair values of derivatives designated as hedging instruments
Notional Amount	$ 20,000	$ 20,000
Derivative Assets, Fair Value
Derivative Liabilities, Fair Value	1,747	1,909
Interest rate swap [Member] | Cash flow hedge [Member]
Notional amounts and fair values of derivatives designated as hedging instruments
Notional Amount	20,000	20,000
Derivative Assets, Fair Value
Other Liabilities [Member] | Interest rate swap [Member] | Cash flow hedge [Member]
Notional amounts and fair values of derivatives designated as hedging instruments
Derivative Liabilities, Fair Value	$ 1,747	$ 1,909