Common shares - Common Share Activities (Detail) - CAD ($) shares in Thousands, $ in Millions |
12 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
||||||||||||||||||||||||||||||||||||||||||||||||
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Common stock beginning balance, (in shares) | 509,045 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Common stock, ending balance, (in shares) | 483,593 | 509,045 | ||||||||||||||||||||||||||||||||||||||||||||||||
| Common stock, beginning balance | [1] | $ 942 | ||||||||||||||||||||||||||||||||||||||||||||||||
| Common stock, ending balance | [1] | $ 895 | $ 942 | |||||||||||||||||||||||||||||||||||||||||||||||
| Common Stock | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Common stock beginning balance, (in shares) | 509,045 | 535,837 | 584,153 | |||||||||||||||||||||||||||||||||||||||||||||||
| Purchases at stated value, (in shares) | (25,452) | (26,792) | (48,316) | |||||||||||||||||||||||||||||||||||||||||||||||
| Common stock, ending balance, (in shares) | 483,593 | 509,045 | 535,837 | |||||||||||||||||||||||||||||||||||||||||||||||
| Common stock, beginning balance | $ 942 | $ 992 | $ 1,079 | |||||||||||||||||||||||||||||||||||||||||||||||
| Purchases at stated value | (47) | (50) | (87) | |||||||||||||||||||||||||||||||||||||||||||||||
| Common stock, ending balance | $ 895 | $ 942 | $ 992 | |||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||
| X | ||||||||||
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
|
| X | ||||||||||
- Definition Number of shares that have been repurchased and retired during the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Details
|