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Nature of Operations and Significant Accounting Policies (Details) carload in Thousands, $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Nov. 30, 2020 USD ($) mi | Dec. 31, 2020 USD ($) employee terminal line_of_business railroad carload port_terminal state mi | Dec. 31, 2019 USD ($) | [1] | Dec. 31, 2018 USD ($) | [1]
Revenue from External Customer [Line Items] |  |  |  |
Number of rail route miles | mi |  | 19,500 |  |
Rail network states number | state |  | 23 |  |
Number of ocean, river and lake ports serviced (over) | port_terminal |  | 70 |  |
Number of short-line and regional railroads served (more than) | railroad |  | 230 |  |
Revenue | $ |  | $ 10,583 | $ 11,937 | $ 12,250
Number of primary lines of business | line_of_business |  | 3 |  |
Number of employees | employee |  | 19,300 |  |
Number of union employees | employee |  | 15,700 |  |
Cost method, maximum percentage |  | 20.00% |  |
Pan Am |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Number of rail route miles | mi | 1,200 |  |  |
Number of partial interests in rail route miles | mi | 600 |  |  |
Pan Am |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Deposit paid to acquire business classified as other investing activities | $ | $ 30 |  |  |
Merchandise business |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Number of carloads | carload |  | 2,500 |  |
Percentage of total volume |  | 43.00% |  |
Percentage of total revenue |  | 67.00% |  |
Intermodal business |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Number of carloads | carload |  | 2,700 |  |
Percentage of total volume |  | 46.00% |  |
Percentage of total revenue |  | 16.00% |  |
Number of terminals | terminal |  | 30 |  |
Coal business |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Number of carloads | carload |  | 637 |  |
Percentage of total volume |  | 11.00% |  |
Percentage of total revenue |  | 13.00% |  |
Other business |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Percentage of total revenue |  | 4.00% |  |
[1] | Certain prior year data has been reclassified to conform to the current presentation.

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