Stock-based Compensation (Expense and Tax Benefits) (Details) - CAD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
|
| Share-based Payment Arrangement, Additional Disclosure [Abstract] | |||
| Total stock-based compensation expense | $ 63 | $ 81 | $ 64 |
| Tax benefit recognized in income | 16 | 18 | 14 |
| Excess tax benefit recognized in income | 14 | 10 | 16 |
| Stock Option Awards [Member] | |||
| Share-based Payment Arrangement, Additional Disclosure [Abstract] | |||
| Total stock-based compensation expense | 8 | 12 | 11 |
| Employee Share Investment Plan [Member] | |||
| Share-based Payment Arrangement, Additional Disclosure [Abstract] | |||
| Total stock-based compensation expense | 23 | 20 | 21 |
| Share Units Plan [Member] | |||
| Share-based Payment Arrangement, Additional Disclosure [Abstract] | |||
| Total stock-based compensation expense | 31 | 47 | 28 |
| Voluntary Incentive Deferral Plan (VIDP) [Member] | |||
| Share-based Payment Arrangement, Additional Disclosure [Abstract] | |||
| Total stock-based compensation expense | $ 1 | $ 2 | $ 4 |