Fair Value of Financial Instruments (Estimated Fair Value And Carrying Amounts) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
5.875% notes due 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	5.875%
3.400% notes due 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.40%
3.950% notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.95%
3.625% notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.625%
4.750% notes due 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.75%
2.750% notes due 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.75%
2.625% notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.625%
2.750% notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.75%
4.750% notes due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.75%
4.250% notes due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.25%
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	$ 9,338,986	$ 9,066,434
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	9,226,611	8,698,464
Global revolving credit facility, net
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	4,700	7,200
Unsecured Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	3,700	4,800
Unsecured Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	16,500	18,500
Deferred financing costs	$ 38,300	37,800
Unsecured Senior Notes | 3.400% notes due 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.40%
Unsecured Senior Notes | 3.950% notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.95%
Unsecured Senior Notes | 3.625% notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.625%
Unsecured Senior Notes | 2.625% notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.625%
Unsecured Senior Notes | 2.750% notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.75%
Unsecured Senior Notes | 4.750% notes due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.75%
Mortgage Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	$ 0	0
Level 2 | Global revolving credit facility, net | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	594,983	558,191
Level 2 | Global revolving credit facility, net | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	594,983	558,191
Level 2 | Unsecured Term Loans | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	1,356,702	1,425,117
Level 2 | Unsecured Term Loans | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	1,356,702	1,425,117
Level 2 | Unsecured Senior Notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	7,280,877	6,976,603
Level 2 | Unsecured Senior Notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	7,168,825	6,608,545
Level 2 | Mortgage Loans | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage Loans	106,424	106,523
Level 2 | Mortgage Loans | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage Loans	$ 106,101	$ 106,611