Derivatives and Hedging Activities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Interest Rate Swap One [Member]
Derivatives and hedging activities
Forecasted Notional Amount	$ 160,000
Variable Interest Rate	3 month LIBOR
Fixed Interest Rate	3.378%
Effective date of interest rate swap agreements	Oct. 21, 2014
Maturity date of interest rate swap agreements	Oct. 21, 2021
Interest Rate Swap Two [Member]
Derivatives and hedging activities
Forecasted Notional Amount	$ 100,000
Variable Interest Rate	3 month LIBOR
Fixed Interest Rate	2.498%
Effective date of interest rate swap agreements	Nov. 30, 2015
Maturity date of interest rate swap agreements	Nov. 30, 2022