Properties - Schedule of Property and Equipment and Weighted Average Estimated Useful Life (Details) - USD ($) |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2024 |
Dec. 31, 2025 |
Dec. 31, 2023 |
Dec. 31, 2024 |
|
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 86,404,000,000 | $ 83,840,000,000 | ||
| Accumulated depreciation | 26,759,000,000 | 25,497,000,000 | ||
| Net book value | 59,645,000,000 | 58,343,000,000 | ||
| Gain recognized in other expense | 0 | $ 0 | ||
| Land | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | 5,471,000,000 | 5,441,000,000 | ||
| Net book value | 5,471,000,000 | 5,441,000,000 | ||
| Total road | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | 63,782,000,000 | 62,049,000,000 | ||
| Accumulated depreciation | 20,630,000,000 | 19,614,000,000 | ||
| Net book value | 43,152,000,000 | 42,435,000,000 | ||
| Rail and other track material | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | 19,747,000,000 | 19,283,000,000 | ||
| Accumulated depreciation | 7,936,000,000 | 7,642,000,000 | ||
| Net book value | $ 11,811,000,000 | $ 11,641,000,000 | ||
| Estimated useful life | 45 years | 46 years | ||
| Ties | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 12,779,000,000 | $ 12,358,000,000 | ||
| Accumulated depreciation | 4,305,000,000 | 4,109,000,000 | ||
| Net book value | $ 8,474,000,000 | $ 8,249,000,000 | ||
| Estimated useful life | 34 years | 34 years | ||
| Ballast | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 6,646,000,000 | $ 6,495,000,000 | ||
| Accumulated depreciation | 2,309,000,000 | 2,182,000,000 | ||
| Net book value | $ 4,337,000,000 | $ 4,313,000,000 | ||
| Estimated useful life | 34 years | 34 years | ||
| Other roadway | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 24,610,000,000 | $ 23,913,000,000 | ||
| Accumulated depreciation | 6,080,000,000 | 5,681,000,000 | ||
| Net book value | $ 18,530,000,000 | $ 18,232,000,000 | ||
| Estimated useful life | 47 years | 47 years | ||
| Total equipment | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 14,324,000,000 | $ 13,750,000,000 | ||
| Accumulated depreciation | 5,460,000,000 | 5,243,000,000 | ||
| Net book value | 8,864,000,000 | 8,507,000,000 | ||
| Locomotives | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | 9,926,000,000 | 9,517,000,000 | ||
| Accumulated depreciation | 3,813,000,000 | 3,724,000,000 | ||
| Net book value | $ 6,113,000,000 | $ 5,793,000,000 | ||
| Estimated useful life | 18 years | 18 years | ||
| Freight cars | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 3,080,000,000 | $ 3,011,000,000 | ||
| Accumulated depreciation | 1,107,000,000 | 1,037,000,000 | ||
| Net book value | $ 1,973,000,000 | $ 1,974,000,000 | ||
| Estimated useful life | 23 years | 22 years | ||
| Work equipment and other | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 1,318,000,000 | $ 1,222,000,000 | ||
| Accumulated depreciation | 540,000,000 | 482,000,000 | ||
| Net book value | $ 778,000,000 | $ 740,000,000 | ||
| Estimated useful life | 17 years | 17 years | ||
| Technology and other | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 1,414,000,000 | $ 1,431,000,000 | ||
| Accumulated depreciation | 669,000,000 | 640,000,000 | ||
| Net book value | $ 745,000,000 | $ 791,000,000 | ||
| Estimated useful life | 12 years | 12 years | ||
| Construction in progress | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Cost | $ 1,413,000,000 | $ 1,169,000,000 | ||
| Accumulated depreciation | 0 | 0 | ||
| Net book value | $ 1,413,000,000 | $ 1,169,000,000 | ||
| Chassis assets | Other Expense | ||||
| Property, Plant and Equipment [Line Items] | ||||
| Gain recognized in other expense | $ 46,000,000 | |||