Derivatives (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
2012 Swap [Member]
Summary of interest rate swap contracts
Beginning of Term	Mar. 13, 2012
End of Term	Mar. 13, 2013
Weighted-Average Notional Amount Over Term Remaining	$ 70,000
Fixed Rate	1.085%
2013 Swap [Member]
Summary of interest rate swap contracts
Beginning of Term	Mar. 13, 2013
End of Term	Mar. 13, 2014
Weighted-Average Notional Amount Over Term Remaining	$ 51,000
Fixed Rate	2.181%