Long Term Debt (Indebtedness Table) (Details) (USD $)	12 Months Ended	9 Months Ended
	Dec. 31, 2011 Line of Credit [Member] Twenty Sixteen [Member] Two Point Nine Percent [Member]	Sep. 30, 2012 Line of Credit [Member] Twenty Sixteen [Member] Four Point Seven Five Percent [Member]	Sep. 30, 2012 Unsecured Debt [Member]	Dec. 31, 2011 Unsecured Debt [Member]	Sep. 30, 2012 Unsecured Debt [Member] Twenty Eighteen [Member] Eight Point Eight Seven Five Percent [Member]	Dec. 31, 2011 Unsecured Debt [Member] Twenty Eighteen [Member] Eight Point Eight Seven Five Percent [Member]	Sep. 30, 2012 Unsecured Debt [Member] Twenty Twentytwo [Member] Seven Point One Two Five Percent [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 85,000,000	$ 5,500,000	$ 970,331,000	$ 798,409,000	$ 714,831,000	$ 713,409,000	$ 250,000,000
Variable Interest Rate	2.90%	4.75%
Fixed Interest Rate					8.875%		7.175%
Unamortized Discount on Debt					$ 10,200,000	$ 11,600,000