Dispositions (Narratives) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended		0 Months Ended			3 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Retail CA Los Angeles Beverly Connection [Member]	Sep. 30, 2013 Retail CA Los Angeles Beverly Connection [Member]	Sep. 30, 2014 Retail CA Los Angeles Beverly Connection [Member]	Sep. 30, 2013 Retail CA Los Angeles Beverly Connection [Member]	Feb. 24, 2014 Retail Properties Segment [Member] Retail NY Hicksville (Broadway Mall) [Member]	Jul. 08, 2014 Retail Properties Segment [Member] Retail CA Los Angeles Beverly Connection [Member] sqft	Mar. 02, 2014 Retail Properties Segment [Member] Retail Springfield Mall [Member] sqft	Mar. 31, 2014 Retail Properties Segment [Member] Retail Springfield Mall [Member]	Mar. 02, 2014 Retail Properties Segment [Member] Retail Springfield Mall [Member] Pennsylevenia Real Estate Investment Trust [Member]	Sep. 30, 2014 Retail And Other Segment Properties [Member]	Sep. 30, 2014 Retail And Other Segment Properties [Member] Properties
Disposal Group Including Discontinued Operation Additional Disclosures [Abstract]
Gross proceeds from the sale of real estate							$ 94,000	$ 260,000	$ 465,000				$ 15,000
Net proceeds from the sale of real estate							92,174
Square Footage Of Real Estate Property								335,000	1,350,000
Net gains on sale of real estate			44,155	0	44,155	0		44,155				13,641
Cash proceeds from the sale of real estate								239,000	340,000
Mortgage loan receivable								21,000
Mortgage loan receivable maturity tenure								10 years
Operating Partnership Units Value Received From Buyer											125,000
Impairment losses	$ 20,842	$ 4,727								$ 20,000
Number Of Real Estate Properties Sold													2