Derivatives and Hedging Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	$ 200,000	$ 200,000
Fair Value	(11,091)	(16,189)
Positions One [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	25,000	25,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	Feb. 16, 2006	Feb. 16, 2006
Effective Date	Dec. 28, 2006	Dec. 28, 2006
Maturity Date	Dec. 28, 2016	Dec. 28, 2016
Current Rate Received	0.25%	0.31%
Pay Fixed Swap Rate	5.04%	5.04%
Fair Value	(3,429)	(4,416)
Positions Two [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	25,000	25,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	Feb. 16, 2006	Feb. 16, 2006
Effective Date	Dec. 28, 2006	Dec. 28, 2006
Maturity Date	Dec. 28, 2016	Dec. 28, 2016
Current Rate Received	0.25%	0.31%
Pay Fixed Swap Rate	5.04%	5.04%
Fair Value	(3,429)	(4,417)
Positions Three [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	25,000	25,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	Dec. 08, 2008	Dec. 08, 2008
Effective Date	Dec. 10, 2008	Dec. 10, 2008
Maturity Date	Dec. 10, 2013	Dec. 10, 2013
Current Rate Received	0.26%	0.31%
Pay Fixed Swap Rate	2.65%	2.65%
Fair Value	(116)	(553)
Positions Four [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	25,000	25,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	Dec. 09, 2008	Dec. 09, 2008
Effective Date	Dec. 10, 2008	Dec. 10, 2008
Maturity Date	Dec. 10, 2013	Dec. 10, 2013
Current Rate Received	0.26%	0.31%
Pay Fixed Swap Rate	2.59%	2.59%
Fair Value	(113)	(539)
Positions Five [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	25,000	25,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	Dec. 09, 2008	Dec. 09, 2008
Effective Date	Dec. 10, 2008	Dec. 10, 2008
Maturity Date	Dec. 10, 2018	Dec. 10, 2018
Current Rate Received	0.26%	0.31%
Pay Fixed Swap Rate	2.94%	2.94%
Fair Value	(1,771)	(2,819)
Positions Six [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	50,000	50,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	Nov. 17, 2009	Nov. 17, 2009
Effective Date	Dec. 20, 2010	Dec. 20, 2010
Maturity Date	Dec. 20, 2014	Dec. 20, 2014
Current Rate Received	0.25%	0.31%
Pay Fixed Swap Rate	3.04%	3.04%
Fair Value	(1,671)	(2,647)
Positions Seven [Member]
Details of derivative positions for interest rate swaps which qualify as hedges for accounting purposes
Notional Amount	25,000	25,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR	3 Month LIBOR
Trade Date	May 05, 2011	May 05, 2011
Effective Date	Jun. 10, 2011	Jun. 10, 2011
Maturity Date	Jun. 10, 2015	Jun. 10, 2015
Current Rate Received	0.26%	0.31%
Pay Fixed Swap Rate	1.71%	1.71%
Fair Value	$ (562)	$ (798)