Mortgage and Other Indebtedness (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011		Dec. 31, 2010
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,145,084
Weighted Average Interest Rate (in hundredths)	4.94%	[1]	4.92%	[1]
Total	5,233,148		5,209,747
Fixed-Rate Debt [Member]
Amount	4,125,280		3,694,742
Weighted Average Interest Rate (in hundredths)	5.64%	[1]	5.85%	[1]
Fixed-Rate Debt [Member] | Non-recourse Loans on Operating Properties [Member]
Amount	4,047,205	[2]	3,664,293	[2]
Weighted Average Interest Rate (in hundredths)	5.63%	[1]	5.85%	[1]
Fixed-Rate Debt [Member] | Recourse Term Loans on Operating Properties [Member]
Amount	78,075		30,449
Weighted Average Interest Rate (in hundredths)	5.89%	[1]	6.00%	[1]
Variable-Rate Debt [Member]
Amount	1,107,868		1,515,005
Weighted Average Interest Rate (in hundredths)	2.35%	[1]	2.65%	[1]
Variable-Rate Debt [Member] | Construction Loans [Member]
Amount	57,061		14,536
Weighted Average Interest Rate (in hundredths)	3.25%	[1]	3.32%	[1]
Variable-Rate Debt [Member] | Secured Lines of Credit [Member]
Amount	215,026		598,244
Weighted Average Interest Rate (in hundredths)	2.99%	[1]	3.38%	[1]
Variable-Rate Debt [Member] | Unsecured Term Loans[Member]
Amount	437,214		437,494
Weighted Average Interest Rate (in hundredths)	1.60%	[1]	1.66%	[1]
Variable-Rate Debt [Member] | Recourse Term Loans on Operating Properties [Member]
Amount	285,067		350,106
Weighted Average Interest Rate (in hundredths)	2.36%	[1]	2.28%	[1]
Variable-Rate Debt [Member] | Non Recourse Term Loans on Operating Properties [Member]
Amount	113,500		114,625
Weighted Average Interest Rate (in hundredths)	3.60%	[1]	3.61%	[1]
Secured Line of Credit 1 [Member]
Line of Credit Facility, Maximum Borrowing Capacity	520,000
Line of Credit Facility, Amount Outstanding	150,196
Secured Line of Credit 3 [Member]
Line of Credit Facility, Maximum Borrowing Capacity	525,000	[3]
Line of Credit Facility, Amount Outstanding	47,130	[3]
Secured Line of Credit Two, Reduced Capacity [Member]
Line of Credit Facility, Maximum Borrowing Capacity	100,084
Secured Line of Credit 2 [Member]
Line of Credit Facility, Maximum Borrowing Capacity	105,000
Line of Credit Facility, Amount Outstanding	$ 17,700

[1] Weighted-average interest rate includes the effect of debt premiums (discounts), but excludes amortization of deferred financing costs.

[2] The Company has four interest rate swaps on notional amounts totaling $118,641 as of September 30, 2011 related to its variable-rate loans on operating properties to effectively fix the interest rate on the respective loans. Therefore, these amounts are reflected in fixed-rate debt in 2011.

[3] There was an additional $4,870 outstanding on this secured line of credit as of September 30, 2011 for letters of credit. Up to $50,000 of the capacity on this line can be used for letters of credit.