Real Estate Activities Real Estate Activities - Impairment of Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Asset Impairments [Line Items]
Asset Impairment Charges	$ 51,412	$ 2,297	$ 86,319	$ 19,695
Impairment of assets and expensed project costs			$ 86,648	$ 20,125
Lycoming Mall [Member]
Schedule of Asset Impairments [Line Items]
Asset Impairment Charges	12,300
Voorhees Town Center [Member]
Schedule of Asset Impairments [Line Items]
Asset Impairment Charges	39,100
Gadsden Mall [Member]
Schedule of Asset Impairments [Line Items]
Asset Impairment Charges	27,300
Uniontown Mall [Member]
Schedule of Asset Impairments [Line Items]
Asset Impairment Charges	$ 7,500