Investments in Real Estate Partnerships - Scheduled Principal Payments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010	Sep. 01, 2010	Jun. 02, 2010	Apr. 30, 2010
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 269,512
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	42,039
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	95,874
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	149,395
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	345,487
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	968,237
Unamortized debt premiums, net	4,236			(47,200)	(202,000)	(514,800)
Equity Method Investment, Summarized Financial Information, Notes Payable	1,874,780		2,117,695
2012	199,375
2013	23,326
2014	185,000
2015	441,482
2016	19,018
Beyond 5 Years	1,112,536
Unamortized debt discounts (premiums)	1,703
Long-term Debt	1,982,440		2,094,469
Scheduled Principal Payments [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	13,876
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	17,666
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	18,505
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	18,599
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	15,730
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	78,156
Unamortized debt premiums, net	0
Equity Method Investment, Summarized Financial Information, Notes Payable	162,532
2012	6,998
2013	6,996
2014	6,481
2015	5,169
2016	4,857
Beyond 5 Years	24,490
Unamortized debt discounts (premiums)	0
Long-term Debt	54,991
Mortgage Loan Maturities [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	234,838
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	24,373
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	77,369
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	130,796
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	329,757
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	890,081
Unamortized debt premiums, net	4,236
Equity Method Investment, Summarized Financial Information, Notes Payable	1,691,450
2012	0
2013	16,330
2014	28,519
2015	46,313
2016	14,161
Beyond 5 Years	288,046
Unamortized debt discounts (premiums)	4,185
Long-term Debt	397,554
Unsecured Maturities [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	20,798
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Equity Method Investment, Summarized Financial Information, Long-term Debt, Maturities, Repayments of Principal After Year Five	0
Unamortized debt premiums, net	0
Equity Method Investment, Summarized Financial Information, Notes Payable	20,798
2012	192,377	[1]
2013	0	[1]
2014	150,000	[1]
2015	390,000	[1]
2016	0	[1]
Beyond 5 Years	800,000	[1]
Unamortized debt discounts (premiums)	(2,482)	[1]
Long-term Debt	1,529,895	[1]
Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
2012	101,896
2013	15,306
2014	28,582
2015	48,258
2016	104,233
Beyond 5 Years	311,245
Unamortized debt discounts (premiums)	910
Long-term Debt	$ 610,430

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