Fair Value of Financial Instruments (Estimated Fair Value And Carrying Amounts) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
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	$ 10,654,307	$ 11,236,731
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	10,343,805	11,181,880
Global revolving credit facilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	14,200	15,400
Unsecured Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	3,900	4,200
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	11,500	19,900
Deferred financing costs	$ 45,700	40,600
Senior Notes | 3.400% notes due 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.40%
Senior Notes | 3.950% notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.95%
Senior Notes | 3.625% notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	3.625%
Senior Notes | 2.625% notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.625%
Senior Notes | 2.750% notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	2.75%
Senior Notes | 4.750% notes due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	4.75%
Secured Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	$ 300	20,200
Level 2 | Global revolving credit facilities | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	857,211	1,663,156
Level 2 | Global revolving credit facilities | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	857,211	1,663,156
Level 2 | Unsecured Term Loans | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	811,654	1,183,121
Level 2 | Unsecured Term Loans | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Lines of credit	811,654	1,183,121
Level 2 | Senior Notes | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	8,879,673	7,684,368
Level 2 | Senior Notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes	8,569,195	7,629,679
Level 2 | Secured Debt | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans	105,769	706,086
Level 2 | Secured Debt | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans	$ 105,745	$ 705,924