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Properties (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 75,620 | $ 75,420
Accumulated depreciation |  | 21,558 | 21,259
Net book value |  | 54,062 | 54,161
Land [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | 5,245 | 5,246
Net book value |  | 5,245 | 5,246
Road: Rail and Other Track Material [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | 17,693 | 17,620
Accumulated depreciation |  | 6,698 | 6,631
Net book value |  | $ 10,995 | $ 10,989
Estimated useful life |  | 43 years | 42 years
Road: Ties [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 11,121 | $ 11,051
Accumulated depreciation |  | 3,387 | 3,331
Net book value |  | $ 7,734 | $ 7,720
Estimated useful life |  | 34 years | 34 years
Road: Ballast [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 5,956 | $ 5,926
Accumulated depreciation |  | 1,785 | 1,753
Net book value |  | $ 4,171 | $ 4,173
Estimated useful life |  | 34 years | 34 years
Road: Other Roadway [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost | [1] | $ 21,058 | $ 21,030
Accumulated depreciation | [1] | 4,386 | 4,329
Net book value | [1] | $ 16,672 | $ 16,701
Estimated useful life | [1] | 48 years | 48 years
Total Road [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 55,828 | $ 55,627
Accumulated depreciation |  | 16,256 | 16,044
Net book value |  | 39,572 | 39,583
Equipment: Locomotives [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | 9,322 | 9,375
Accumulated depreciation |  | 3,605 | 3,555
Net book value |  | $ 5,717 | $ 5,820
Estimated useful life |  | 17 years | 17 years
Equipment: Freight Cars [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 2,157 | $ 2,118
Accumulated depreciation |  | 801 | 789
Net book value |  | $ 1,356 | $ 1,329
Estimated useful life |  | 25 years | 25 years
Equipment: Work Equipment and Other [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 1,108 | $ 1,107
Accumulated depreciation |  | 361 | 351
Net book value |  | $ 747 | $ 756
Estimated useful life |  | 18 years | 18 years
Total Equipment [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 12,587 | $ 12,600
Accumulated depreciation |  | 4,767 | 4,695
Net book value |  | 7,820 | 7,905
Technology and Other [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | 1,211 | 1,199
Accumulated depreciation |  | 535 | 520
Net book value |  | $ 676 | $ 679
Estimated useful life |  | 12 years | 13 years
Construction in Progress [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Cost |  | $ 749 | $ 748
Net book value |  | $ 749 | $ 748
[1] | Other roadway includes grading, bridges and tunnels, signals, buildings, and other road assets.

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