Fair Value Of Instruments (Estimated Fair Value And Carrying Amounts) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other secured loan	$ 10,500		$ 10,500
Unamortized discount	8,681
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Global revolving credit facility	678,554	[1]	275,106	[1]
Unsecured senior notes	1,540,111	[2],[3]	1,502,271	[2],[3]
Exchangeable senior debentures	484,057	[2]	438,327	[2]
Mortgage Loans	939,756	[2]	1,007,615	[2]
Other secured loan	10,699		10,688
Long-term Debt	3,653,177		3,234,007
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Global revolving credit facility	678,554	[1]	275,106	[1]
Unsecured senior notes	1,441,319	[2],[3]	1,441,072	[2],[3]
Exchangeable senior debentures	266,400	[2]	266,400	[2]
Mortgage Loans	875,075	[2]	947,132	[2]
Other secured loan	10,500		10,500
Long-term Debt	3,271,848		2,940,210
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized discount	$ 8,681		$ 8,928

[1] 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.

[2] 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.

[3] The carrying value of the 2015 Notes, 2020 Notes and 2021 Notes are net of discount of $8,681 and $8,928 in the aggregate as of March 31, 2012 and December 31, 2011, respectively.