Financial Derivative Instruments (Details) (USD $)				3 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Interest Rate Swap Agreement [Member]	Jun. 30, 2012 Interest Rate Swap Agreement [Member] Interest Expense [Member]	Jun. 30, 2011 Interest Rate Swap Agreement [Member] Interest Expense [Member]	Jun. 30, 2012 Interest Rate Swap Agreement [Member] Interest Expense [Member]	Jun. 30, 2011 Interest Rate Swap Agreement [Member] Interest Expense [Member]	Jun. 30, 2012 Interest Rate Swap September 2014 [Member] Interest Rate Swap Agreement [Member] Cash Flow Hedging [Member]	Jun. 30, 2012 Interest Rate Swap March 2015 [Member] Interest Rate Swap Agreement [Member] Cash Flow Hedging [Member]	Jun. 30, 2012 Interest Rate Swap September 2015 [Member] Interest Rate Swap Agreement [Member] Cash Flow Hedging [Member]
Interest-Rate Swap Agreement [Line Items]
Coverage Amount			$ 72,000,000					$ 24,000,000	$ 24,000,000	$ 24,000,000
Variable Interest Rate (in hundredths)								1.66%	1.91%	2.14%
Derivative, Fair Value [Line Items]
Fair value of derivatives, net liability	2,633,000	2,469,000
Derivative Instruments, Gain (Loss) [Line Items]
Increase (decrease) in interest expense				$ 117,000	$ 575,000	$ 164,000	$ 236,000