Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 3,575	$ 3,566
3.60% Senior Notes Due 2022 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 250	249
Stated interest rate (percent)	3.60%
3.6% Senior Notes Due 2026 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 744	744
Stated interest rate (percent)	3.60%
Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 11	11
1.625% Senior Notes Due 2029 \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 822	849
Stated interest rate (percent)	1.625%
3.375% Senior Notes Due 2030 \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 296	296
Stated interest rate (percent)	3.375%
3.50% Senior Notes Due 2032 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 249	249
Stated interest rate (percent)	3.50%
5.0% Senior Notes Due 2046 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 678	677
Stated interest rate (percent)	5.00%
4.375% Senior Notes Due 2047 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 491	491
Stated interest rate (percent)	4.375%
8.73% Senior Notes Due 2022 \| Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate (percent)	8.73%
8.73% Senior Notes Due 2022 \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 30	0
Stated interest rate (percent)	8.73%
Term Loan Due Twenty Twenty Six \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 4	0
Stated interest rate (percent)	0.20%
Fair Value [Member] \| 3.60% Senior Notes Due 2022 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 256	259
Fair Value [Member] \| 3.6% Senior Notes Due 2026 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	818	846
Fair Value [Member] \| Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	11	11
Fair Value [Member] \| 1.625% Senior Notes Due 2029 \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	872	897
Fair Value [Member] \| 3.375% Senior Notes Due 2030 \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	324	332
Fair Value [Member] \| 3.50% Senior Notes Due 2032 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	273	276
Fair Value [Member] \| 5.0% Senior Notes Due 2046 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	881	905
Fair Value [Member] \| 4.375% Senior Notes Due 2047 [Member] \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	585	597
Fair Value [Member] \| 8.73% Senior Notes Due 2022 \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	30	0
Fair Value [Member] \| Term Loan Due Twenty Twenty Six \| Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 4	$ 0

Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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