Derivative Instruments and Hedging Activities - Income Statement Items for Derivatives not Designated as Hedging Instruments (Details 2) (Not designated as hedging instruments [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income for derivatives not designated as hedging instruments
Income for derivatives not designated as hedging instruments	$ 715	$ (23)	$ 644
Net gain (loss) on mortgage banking activities [Member] | Interest rate locks with customers [Member]
Income for derivatives not designated as hedging instruments
Income for derivatives not designated as hedging instruments	467	549	506
Net gain (loss) on mortgage banking activities [Member] | Forward loan sale commitments [Member]
Income for derivatives not designated as hedging instruments
Income for derivatives not designated as hedging instruments	$ 248	$ (572)	$ 138