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	Sep. 30, 2013		Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	$ 4,468,069		$ 3,102,485
Mezzanine notes payable	311,340		0
Unsecured senior notes	5,835,424		4,639,528
Unsecured exchangeable senior notes	739,536		1,170,356
Impact of accounting pronouncement	(7,409)
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	4,468,069		3,102,485
Mezzanine notes payable	311,340		0
Unsecured senior notes	5,835,424		4,639,528
Unsecured exchangeable senior notes	739,536	[1]	1,170,356	[1]
Total	11,354,369		8,912,369
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	4,592,273		3,256,940
Mezzanine notes payable	311,366		0
Unsecured senior notes	6,065,723		5,162,486
Unsecured exchangeable senior notes	768,019		1,278,554
Total	11,737,381		9,697,980
ASC 470-20 Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Impact of accounting pronouncement	$ 7,400		$ 25,500

[1] Includes the net adjustment for the equity component allocation totaling approximately $7.4 million and $25.5 million at September 30, 2013 and December 31, 2012, respectively.