Investments In Unconsolidated Joint Ventures (Balance Sheets Of The Unconsolidated Joint Ventures) (Details) (USD $) In Thousands	Sep. 30, 2011		Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]
Real estate and development in process, net	$ 10,639,176		$ 10,441,117
Mortgage and notes payable	3,179,034		3,047,586
Other liabilities	244,555		213,000
Total liabilities and members'/partners' equity	13,980,798		13,348,263
Carrying value of the Company's investments in unconsolidated joint ventures	770,466		767,252
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Real estate and development in process, net	4,991,083		5,028,851
Other assets	680,091		749,308
Total assets	5,671,174		5,778,159
Mortgage and notes payable	3,139,362		3,151,220
Other liabilities	907,144		969,082
Members'/Partners' equity	1,624,668		1,657,857
Total liabilities and members'/partners' equity	5,671,174		5,778,159
Company's share of equity	898,910		924,235
Basis differentials	(128,444)	[1]	(156,983)	[1]
Carrying value of the Company's investments in unconsolidated joint ventures	$ 770,466		$ 767,252

[1] This amount represents the aggregate difference between the Company's historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from impairment of investments and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level.