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Fair Value Measurements (Schedule Of Carrying And Fair Values Of Long-Term Debt) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Jul. 17, 2019
--- | --- | --- | ---
Senior Notes [Member] | 3.60% Senior Notes Due 2022 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 249 | $ 249 |
Stated interest rate (percent) | 3.60% |  |
Senior Notes [Member] | 3.60% Senior Notes Due 2026 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 744 | 742 |
Stated interest rate (percent) | 3.60% |  |
Senior Notes [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 11 | 11 |
Senior Notes [Member] | 1.625% Senior Notes Due 2029 |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 849 | 774 | $ 779
Stated interest rate (percent) | 1.625% |  |
Senior Notes [Member] | 6 1/2% GO Zone Senior Notes Due 2029 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 0 | 99 |
Stated interest rate (percent) | 6.50% |  |
Senior Notes [Member] | 3.375 Senior Notes Due 2030 |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 296 | 0 |
Stated interest rate (percent) | 3.375% |  |
Senior Notes [Member] | 3.50% Senior Notes Due 2032 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 249 | 249 |
Stated interest rate (percent) | 3.50% |  |
Senior Notes [Member] | 6 1/2% GO Zone Senior Notes Due 2035 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 0 | 88 |
Stated interest rate (percent) | 6.50% |  |
Senior Notes [Member] | 6.5% 2035 IKE Zone Senior Notes [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 0 | 65 |
Stated interest rate (percent) | 6.50% |  |
Senior Notes [Member] | 5.0% 2046 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 677 | 677 |
Stated interest rate (percent) | 5.00% |  |
Senior Notes [Member] | 4.375% Senior Notes Due 2047 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term Debt | $ 491 | 491 |
Stated interest rate (percent) | 4.375% |  |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 3.60% Senior Notes Due 2022 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | $ 259 | 255 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 3.60% Senior Notes Due 2026 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 846 | 777 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 1.625% Senior Notes Due 2029 |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 897 | 785 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 6 1/2% GO Zone Senior Notes Due 2029 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 0 | 103 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 3.375 Senior Notes Due 2030 |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 332 | 0 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 3.50% Senior Notes Due 2032 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 276 | 267 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 6 1/2% GO Zone Senior Notes Due 2035 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 0 | 92 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 6.5% 2035 IKE Zone Senior Notes [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 0 | 68 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 5.0% 2046 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 905 | 761 |
Estimate of Fair Value Measurement [Member] | Senior Notes [Member] | 4.375% Senior Notes Due 2047 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | 597 | 505 |
Estimate of Fair Value Measurement [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Senior notes | $ 11 | $ 11 |

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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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