Property, plant and equipment - Depreciation expense (Detail) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Property, Plant and Equipment [Line Items] | ||
| Depreciation expense | $ 4,982 | $ 4,779 |
| Insurance and Other [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Depreciation expense | 1,568 | 1,535 |
| Railroad, Utilities and Energy [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Depreciation expense | $ 3,414 | $ 3,244 |