Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Real estate and development in process, net	$ 15,575,438		$ 15,688,744
Mortgage and notes payable	4,289,120		4,309,484
Other liabilities	483,762		502,255
Total liabilities and equity	19,179,071		19,886,767
Carrying value of the Company's investments in unconsolidated joint ventures	196,188		193,394
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Real estate and development in process, net	1,036,221		1,034,552
Other assets	224,398		264,097
Total assets	1,260,619		1,298,649
Mortgage and notes payable	831,039		830,075
Other liabilities	38,500		34,211
Members'/Partners' equity	391,080		434,363
Total liabilities and equity	1,260,619		1,298,649
Company's share of equity	201,037		209,828
Basis differentials	(27,594)	[1]	(27,786)	[1]
Carrying value of the Company's investments in unconsolidated joint ventures	173,443	[2],[3]	182,042	[2]
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of the Company's investments in unconsolidated joint ventures	$ (22,700)		$ (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] (2)Investments with deficit balances aggregating approximately $22.7 million and $11.4 million at March 31, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.

[3] (1)Investments with deficit balances aggregating approximately $22.7 million have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.