Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	$ 2,946,760		$ 3,123,267
Unsecured senior notes	3,865,369		3,865,186
Unsecured exchangeable senior notes	1,148,497		1,715,685
Net of the adjustment for the equity component allocation	46,283
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	2,946,760		3,123,267
Unsecured senior notes	3,865,369		3,865,186
Unsecured exchangeable senior notes	1,148,497	[1]	1,715,685	[1]
Total	7,960,626		8,704,138
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	3,060,477		3,297,903
Unsecured senior notes	4,185,434		4,148,461
Unsecured exchangeable senior notes	1,328,799		1,904,115
Total	8,574,710		9,350,479
ASC 470-20 Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Net of the adjustment for the equity component allocation	$ 46,300		$ 54,500

[1] Includes the net impact of Accounting Standards Codification ("ASC") ASC 470-20 totaling approximately $46.3 million and $54.5 million at March 31, 2012 and December 31, 2011, respectively.