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Commitments And Contingencies (Commitments And Contingencies Activity) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Commitments and Contingencies [Line Items] |  |  |
Current portion, ending balance at December 31 | $ 177 | $ 190 |
Environmental [Abstract] |  |  |
Beginning balance. | 227 | 223 | $ 196
Accruals | 76 | 67 | 84
Payments | (70) | (63) | (57)
Ending balance at December 31 | 233 | 227 | 223
Current portion, ending balance at December 31 | 65 | 62 | 59
Personal Injury [Member] |  |  |
Commitments and Contingencies [Line Items] |  |  |
Beginning balance | 265 | 271 | 285
Current year accruals | 72 | 78 | 74
Changes in estimates for prior years | (3) | (11) | (16)
Payments | (64) | (73) | (72)
Ending balance at December 31 | 270 | 265 | 271
Current portion, ending balance at December 31 | $ 60 | $ 63 | $ 72

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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 + Details
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