Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Real estate and development in process, net		$ 15,612,331	$ 15,688,744
Mortgage and notes payable		4,269,808	4,309,484
Other liabilities		448,480	502,255
Total liabilities and equity		19,113,959	19,886,767
Carrying value of the Company's investments in unconsolidated joint ventures		209,974	193,394
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Real estate and development in process, net		1,038,567	1,034,552
Other assets		243,773	264,097
Total assets		1,282,340	1,298,649
Mortgage and notes payable		832,860	830,075
Other liabilities		35,483	34,211
Members'/Partners' equity		413,997	434,363
Total liabilities and equity		1,282,340	1,298,649
Company's share of equity		212,065	209,828
Basis differentials	[1]	(27,418)	(27,786)
Carrying value of the Company's investments in unconsolidated joint ventures	[2],[3]	184,647	182,042
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of the Company's investments in unconsolidated joint ventures		$ (25,300)	$ (11,400)

[1] (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.

[2] (1)Investments with deficit balances aggregating approximately $25.3 million and $11.4 million at June 30, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.

[3] (2)Investments with deficit balances aggregating approximately $25.3 million and $11.4 million at June 30, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.