Property, plant and equipment - Depreciation expense (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Property, Plant and Equipment [Line Items] | ||
| Depreciation expense | $ 2,690 | $ 2,449 |
| Insurance and Other [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Depreciation expense | 922 | 784 |
| Railroad, Utilities and Energy [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Depreciation expense | $ 1,768 | $ 1,665 |