Fair Value Of Instruments (Estimated Fair Value And Carrying Amounts) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	$ 2,422,322	[1],[2]	$ 2,379,999	[1],[2]
Exchangeable senior debentures	363,846	[1]	336,847	[1]
Mortgage Loans	589,378	[1]	622,580	[1]
Long-term Debt	5,192,937		5,085,078
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	2,368,848	[1],[2]	2,364,232	[1],[2]
Exchangeable senior debentures	266,400	[1]	266,400	[1]
Mortgage Loans	554,742	[1]	585,608	[1]
Long-term Debt	5,007,381		4,961,892
Global Revolving Credit Facility [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	790,500	[3]	724,668	[3]
Global Revolving Credit Facility [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	790,500	[3]	724,668	[3]
Unsecured Term Loan [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	1,026,891	[4]	1,020,984	[4]
Unsecured Term Loan [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	1,026,891	[4]	1,020,984	[4]
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 14,632		$ 15,047

[1] Valuations for our unsecured senior notes and mortgage loans are determined based on the expected future payments discounted at risk-adjusted rates. The 2015 Notes, 2020 Notes, 2021 Notes, 2022 Notes and 2025 Notes and exchangeable senior debentures are valued based on quoted market prices.

[2] The carrying value of the 2015 Notes, 2020 Notes, 2021 Notes, 2022 Notes and 2025 Notes are net of discount of $14,632 and $15,047 in the aggregate as of March 31, 2014 and December 31, 2013, respectively.

[3] The carrying value of our global revolving credit facility approximates estimated fair value, due to the variability of interest rates and the stability of our credit rating.

[4] The carrying value of our unsecured term loan approximates estimated fair value, due to the variability of interest rates and the stability of our credit rating.