Subsequent Events (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended					9 Months Ended			3 Months Ended	9 Months Ended			3 Months Ended			3 Months Ended	9 Months Ended		3 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Nov. 30, 2012	Dec. 31, 2012 Preferred stock, shares outstanding Series C	Sep. 30, 2012 Preferred stock, shares outstanding Series C	Nov. 05, 2012 Preferred stock, shares outstanding Series C	Dec. 31, 2011 Preferred stock, shares outstanding Series C	Dec. 31, 2012 Series E Preferred Stock [Member]	Sep. 30, 2012 Unsecured Line of Credit 1 [Member]	Nov. 30, 2012 Unsecured Line of Credit 1 [Member]	Sep. 30, 2012 Unsecured Line of Credit 2 [Member]	Sep. 30, 2012 Unsecured Line of Credit 2 [Member]	Nov. 30, 2012 Unsecured Line of Credit 2 [Member]	Dec. 31, 2012 Hickory Hollow Mall [Member]	Dec. 31, 2012 Towne Mall [Member]
Subsequent Event [Line Items]
Gross sales price		$ 7,803																	$ 1,000	$ 950
Net proceeds from sale		7,432																	966	892
Mortgage Loans on Real Estate, New Mortgage Loans			342,190
Debt Instrument, Description of Variable Rate Basis		LIBOR plus a range of 155 to 210 basis points
Line of Credit Facility, Increase, Additional Borrowings		155,000
Line of Credit Facility, Maximum Borrowing Capacity								1,200,000							600,000	228,000	228,000	600,000
Debt Instrument, Maturity Date														Nov. 01, 2015		Nov. 01, 2016	Apr. 22, 2013
Loss on impairment of real estate		21,654			51,304	21,654	51,304
Extinguishment of Debt, Amount	106,895	121,980	30,763	381,568
Secured Convertible Notes Receivable		4,875				4,875
Stock Issued During Period, Shares, New Issues	2,465,442												6,900,000
Preferred Stock, Dividend Rate, Percentage										0.00%			6.625%
Payments for Repurchase of Preferred Stock and Preference Stock									115,000
Preferred Stock Liquidation Preference, Depositary Shares											$ 25.00
Net Proceeds from Sale of Preferred Stock, Depositary Shares													166,636
Preferred Stock, Redemption Amount											115,891
Partial Pay Down on Line of Credit Facility Outstanding Balance	50,745
Preferred Stock, Dividend Rate, Per-Dollar-Amount													$ 1.65625
Preferred stock, shares outstanding										460,000		460,000
Accrued dividends and distributions payable		43,547			41,717	43,547	41,717				891
Unamortized Stock Issuance Costs Written Off									$ 3,773