Derivatives and Hedging Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Interest Rate Swap One [Member]
Summary of interest rate derivative financial instruments
Forecasted notional amount	$ 160,000
Interest rate swap, counterparty variable interest rate	3 month LIBOR
Interest rate swap, 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]
Summary of interest rate derivative financial instruments
Forecasted notional amount	$ 100,000
Interest rate swap, counterparty variable interest rate	3 month LIBOR
Interest rate swap, 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