Debt (Credit Facility) (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Principal amount	$ 8,470,678,000			$ 8,348,775,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Principal amount	300,000,000	$ 300,000,000.0		$ 0
Credit facility, remaining borrowing capacity	$ 696,800,000
Term Loan Facility
Line of Credit Facility [Line Items]
Quarter periodic payment, percent	0.25%
2017 credit agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Principal amount	$ 1,000,000,000.0
Commitments not extended	76,000,000.0		$ 76,000,000.0
Term Loan Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Principal amount	$ 3,415,000,000.0
London Interbank Offered Rate (LIBOR) | Term Loan Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Basis spread on variable rate	4.25%
Basis spread on variable rate, floor	0.75%
London Interbank Offered Rate (LIBOR) | Minimum | Revolving Credit Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
London Interbank Offered Rate (LIBOR) | Maximum | Revolving Credit Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Basis spread on variable rate	3.00%
Base Rate | Term Loan Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Basis spread on variable rate	3.25%
Basis spread on variable rate, floor	1.75%
Base Rate | Minimum | Revolving Credit Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Base Rate | Maximum | Revolving Credit Facility | 2017 credit agreement
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.00%