Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
ASSETS
Real estate and development in process, net		$ 15,555,641	$ 15,688,744
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable		3,438,714	4,309,484
Other liabilities		483,601	502,255
Total liabilities and equity / capital		18,379,456	19,886,767
Carrying value of the Company's investments in unconsolidated joint ventures		235,224	193,394
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net		1,072,412	1,034,552
Other assets		256,055	264,097
Total assets		1,328,467	1,298,649
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable		833,895	830,075
Other liabilities		44,549	34,211
Members'/Partners' equity		450,023	434,363
Total liabilities and equity / capital		1,328,467	1,298,649
Company's share of equity		237,070	209,828
Basis differentials	[1]	(27,047)	(27,786)
Carrying value of the Company's investments in unconsolidated joint ventures	[2]	210,023	182,042
Unconsolidated Joint Ventures [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Carrying value of the Company's investments in unconsolidated joint ventures		$ (25,200)	$ (11,400)

[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] Investments with deficit balances aggregating approximately $25.2 million and $11.4 million at December 31, 2015 and 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.