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Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 12, 2020	Dec. 31, 2019	Jul. 31, 2010
Debt Instrument [Line Items]
Principal Amount	$ 3,801		$ 3,500
Unamortized Premium (Discount) and Debt Issuance Costs	(56)		(55)
Net, Long-term Debt	$ 3,745		3,445
Senior Notes [Member] \| 3.60% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2022
Stated interest rate (percent)	3.60%
Principal Amount	$ 250		250
Unamortized Premium (Discount) and Debt Issuance Costs	(1)		(1)
Net, Long-term Debt	$ 249		249
Senior Notes [Member] \| 3.6% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2026
Stated interest rate (percent)	3.60%
Principal Amount	$ 750		750
Unamortized Premium (Discount) and Debt Issuance Costs	(7)		(8)
Net, Long-term Debt	$ 743		742
Senior Notes [Member] \| Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2027
Principal Amount	$ 11		11
Unamortized Premium (Discount) and Debt Issuance Costs	0		0
Net, Long-term Debt	$ 11		11
Senior Notes [Member] \| 1.625% Senior Notes Due 2029
Debt Instrument [Line Items]
Debt Instrument Maturity	2029
Stated interest rate (percent)	1.625%
Principal Amount	$ 786		785
Unamortized Premium (Discount) and Debt Issuance Costs	(10)		(11)
Net, Long-term Debt	$ 776		774
Senior Notes [Member] \| 6 1/2% GO Zone Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2029
Stated interest rate (percent)	6.50%
Principal Amount	$ 100		100	$ 100
Unamortized Premium (Discount) and Debt Issuance Costs	0		(1)
Net, Long-term Debt	$ 100		99
Senior Notes [Member] \| 3.375% Senior Notes Due 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2030
Stated interest rate (percent)	3.375%
Principal Amount	$ 300	$ 300	0
Unamortized Premium (Discount) and Debt Issuance Costs	(4)		0
Net, Long-term Debt	$ 296		0
Senior Notes [Member] \| 3.50% Senior Notes Due 2032 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2032
Stated interest rate (percent)	3.50%
Principal Amount	$ 250		250
Unamortized Premium (Discount) and Debt Issuance Costs	(1)		(1)
Net, Long-term Debt	$ 249		249
Senior Notes [Member] \| 2035 GO Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
Principal Amount	$ 89		89
Unamortized Premium (Discount) and Debt Issuance Costs	(1)		(1)
Net, Long-term Debt	$ 88		88
Senior Notes [Member] \| 2035 IKE Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
Principal Amount	$ 65		65
Unamortized Premium (Discount) and Debt Issuance Costs	0		0
Net, Long-term Debt	$ 65		65
Senior Notes [Member] \| 5.0% Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2046
Stated interest rate (percent)	5.00%
Principal Amount	$ 700		700
Unamortized Premium (Discount) and Debt Issuance Costs	(23)		(23)
Net, Long-term Debt	$ 677		677
Senior Notes [Member] \| 4.375% Senior Notes Due 2047 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2047
Stated interest rate (percent)	4.375%
Principal Amount	$ 500		500
Unamortized Premium (Discount) and Debt Issuance Costs	(9)		(9)
Net, Long-term Debt	$ 491		$ 491