Fair Value Of Instruments (Estimated Fair Value And Carrying Amounts) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other secured loan			$ 10,500
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	1,566,087	[1],[2]	1,502,271	[1],[2]
Exchangeable senior debentures	491,740	[1]	438,327	[1]
Mortgage Loans	895,934	[1]	1,007,615	[1]
Other secured loan			10,688
Long-term Debt	3,799,179		3,234,007
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	1,441,569	[1],[2]	1,441,072	[1],[2]
Exchangeable senior debentures	266,400	[1]	266,400	[1]
Mortgage Loans	846,825	[1]	947,132	[1]
Other secured loan			10,500
Long-term Debt	3,400,212		2,940,210
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized discount	8,430		8,928
Global Revolving Credit Facility [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	324,476	[3]	275,106	[3]
Global Revolving Credit Facility [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	324,476	[3]	275,106	[3]
Unsecured Term Loan [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	520,942
Unsecured Term Loan [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	$ 520,942

[1] Valuations for our unsecured senior notes, mortgage loans and other secured loan are determined based on the expected future payments discounted at risk-adjusted rates. The 2015 Notes, 2020 Notes, 2021 Notes and exchangeable senior debentures are valued based on quoted market prices.

[2] The carrying value of the 2015 Notes, 2020 Notes and 2021 Notes are net of discount of $8,430 and $8,928 in the aggregate as of June 30, 2012 and December 31, 2011, respectively.

[3] The carrying value of our global revolving credit facility approximates estimated fair value, due to the short-term nature of this instrument along with the variability of interest rates.