Real Estate Activities Real Estate Activities - Impairment of Assets (Details) (USD $)	9 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Nittany Mall [Member]	Jun. 30, 2014 Nittany Mall [Member]	Sep. 30, 2014 Nittany Mall [Member]	Mar. 31, 2014 South Mall [Member]	Sep. 30, 2014 North Hanover Mall [Member]	Jun. 30, 2014 North Hanover Mall [Member]	Sep. 30, 2014 North Hanover Mall [Member]	Dec. 31, 2013 North Hanover Mall [Member]	Dec. 31, 2011 North Hanover Mall [Member]
Impairment Of Assets			$ 1,600,000	$ 13,900,000	$ 15,500,000	$ 1,300,000	$ 700,000	$ 2,200,000	$ 2,900,000	$ 6,300,000	$ 24,100,000
Impairment of assets and expensed project costs	$ 20,125,000	$ 30,416,000