Business combinations - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2024 |
Mar. 31, 2024 |
|
| Disclosure of detailed information about business combination [Line Items] | ||||
| Gain on sale of assets | $ 0 | $ 1 | ||
| Cariboo Pulp & Paper Company | ||||
| Disclosure of detailed information about business combination [Line Items] | ||||
| Proportion of ownership interest in joint operation | 50.00% | 100.00% | 50.00% | |
| Gain on sale of assets | $ 1 | |||
| Cariboo Pulp & Paper Company | ||||
| Disclosure of detailed information about business combination [Line Items] | ||||
| Percentage of voting equity interests acquired | 50.00% | |||