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Commitments And Contingencies (Commitments And Contingencies Activity) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
Liability Activity [Abstract] |  |
Current portion, ending balance at March 31 | $ 177 |
Environmental [Abstract] |  |
Beginning balance. | 227 | $ 223
Accruals | 15 | 10
Payments | (16) | (17)
Ending balance at March 31. | 226 | 216
Current portion, ending balance at March 31. | 64 | 63
Personal Injury [Member] |  |
Liability Activity [Abstract] |  |
Beginning balance | 265 | 271
Current year accruals | 18 | 18
Changes in estimates for prior years | 2 | (2)
Payments | (15) | (21)
Ending balance at March 31 | 270 | 266
Current portion, ending balance at March 31 | $ 62 | $ 67

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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=118942415&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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