Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) (USD $)
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Mar. 31, 2013
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Dec. 31, 2012
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Summary Of Significant Accounting Policies [Line Items] | ||||||
Mortgage notes payable | $ 3,053,798,000 | $ 3,102,485,000 | ||||
Unsecured senior notes | 4,639,843,000 | 4,639,528,000 | ||||
Unsecured exchangeable senior notes | 1,177,877,000 | 1,170,356,000 | ||||
Carrying Amount [Member]
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Summary Of Significant Accounting Policies [Line Items] | ||||||
Mortgage notes payable | 3,053,798,000 | 3,102,485,000 | ||||
Unsecured senior notes | 4,639,843,000 | 4,639,528,000 | ||||
Unsecured exchangeable senior notes | 1,177,877,000 | [1] | 1,170,356,000 | [1] | ||
Total | 8,871,518,000 | 8,912,369,000 | ||||
Estimated Fair Value [Member]
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Summary Of Significant Accounting Policies [Line Items] | ||||||
Mortgage notes payable | 3,203,402,000 | 3,256,940,000 | ||||
Unsecured senior notes | 5,194,150,000 | 5,162,486,000 | ||||
Unsecured exchangeable senior notes | 1,235,835,000 | 1,278,554,000 | ||||
Total | 9,633,387,000 | 9,697,980,000 | ||||
ASC 470-20 Adjustment [Member]
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Summary Of Significant Accounting Policies [Line Items] | ||||||
Impact of accounting pronouncement | $ 18,300,000 | $ 25,500,000 | ||||
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