Debt - Schedule of Outstanding Debt (Details) - USD ($)		Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Short-term debt		$ 334,000,000	$ 155,000,000
Outstanding Principal		4,312,000,000	4,405,000,000
Premium (Discount)	[1]	(8,000,000)	(7,000,000)
Total Debt		4,304,000,000	4,398,000,000
Less: Unamortized debt expense	[2]	(20,000,000)	(23,000,000)
Total long-term debt		3,950,000,000	3,969,000,000
2019 Term Loan Agreement | 2019 Term Loan Agreement
Debt Instrument [Line Items]
Outstanding Principal		800,000,000	800,000,000
Premium (Discount)	[1]	0	0
Total Debt		800,000,000	800,000,000
Senior Notes | 2024 Notes
Debt Instrument [Line Items]
Outstanding Principal		600,000,000	600,000,000
Premium (Discount)	[1]	0	0
Total Debt		600,000,000	600,000,000
Senior Notes | 2027 Notes
Debt Instrument [Line Items]
Outstanding Principal		700,000,000	700,000,000
Premium (Discount)	[1]	(2,000,000)	(2,000,000)
Total Debt		698,000,000	698,000,000
Senior Notes | 2028 Notes
Debt Instrument [Line Items]
Outstanding Principal		800,000,000	800,000,000
Premium (Discount)	[1]	(5,000,000)	(5,000,000)
Total Debt		795,000,000	795,000,000
Senior Notes | 2029 Notes
Debt Instrument [Line Items]
Outstanding Principal		547,000,000	550,000,000
Premium (Discount)	[1]	(1,000,000)	(1,000,000)
Total Debt		546,000,000	549,000,000
Senior Notes | 2044 Notes
Debt Instrument [Line Items]
Outstanding Principal		531,000,000	550,000,000
Premium (Discount)	[1]	0	0
Total Debt		531,000,000	550,000,000
Senior Notes | EOIT Senior Notes | EOIT
Debt Instrument [Line Items]
Outstanding Principal		0	250,000,000
Premium (Discount)	[1]	0	1,000,000
Total Debt		0	251,000,000
Senior Notes | Senior notes due in 2020
Debt Instrument [Line Items]
Less: Current portion of long-term debt	[3]	0	251,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding Principal		0	0
Premium (Discount)	[1]	0	0
Total Debt		0	0
Unamortized debt expense related to Revolving Credit Facility		3,000,000	3,000,000
Commercial Paper
Debt Instrument [Line Items]
Short-term debt	[4]	334,000,000	155,000,000
Premium (Discount)	[1]	$ 0	$ 0

[1] Unamortized premium (discount) on long-term debt is amortized over the life of the respective debt.

[2] As of September 30, 2020 and December 31, 2019, there was an additional $3 million and $4 million, respectively, of unamortized debt expense related to the Revolving Credit Facility included in Other assets, not included above.

[3] As of December 31, 2019, Current portion of long-term debt included $251 million outstanding balance of the EOIT Senior Notes which were repaid in March 2020.

[4] Short-term debt includes $334 million and $155 million of outstanding commercial paper as of September 30, 2020 and December 31, 2019, respectively.