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	Jun. 30, 2013		Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	$ 4,484,657		$ 3,102,485
Mezzanine notes payable	311,637		0
Unsecured senior notes	5,834,973		4,639,528
Unsecured exchangeable senior notes	734,278		1,170,356
Impact of accounting pronouncement	(12,298)
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	4,484,657		3,102,485
Mezzanine notes payable	311,637		0
Unsecured senior notes	5,834,973		4,639,528
Unsecured exchangeable senior notes	734,278	[1]	1,170,356	[1]
Total	11,365,545		8,912,369
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	4,598,927		3,256,940
Mezzanine notes payable	311,665		0
Unsecured senior notes	6,093,237		5,162,486
Unsecured exchangeable senior notes	772,691		1,278,554
Total	11,776,520		9,697,980
ASC 470-20 Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Impact of accounting pronouncement	$ 12,300		$ 25,500

[1] Includes the net adjustment for the equity component allocation totaling approximately $12.3 million and $25.5 million at June 30, 2013 and December 31, 2012, respectively.