Debt (Credit Facility) (Narrative) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Principal amount	$ 8,403,949,000	$ 8,470,678,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Principal amount	300,000,000	$ 300,000,000
Credit facility, remaining borrowing capacity	696,300,000
2017 credit agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Principal amount	1,000,000,000.0
Term Loan Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Principal amount	$ 3,415,000,000.0