Debt (Bilateral Letter of Credit Facilities) (Details) - CAD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2022 |
Dec. 31, 2021 |
|
| Bilateral Letter Of Credit Facilities [Member] | ||
| Line of Credit Facility [Line Items] | ||
| Minimum term for which collateral in the form of cash and cash equivalents is pledged for | 1 month | |
| Committed Bilateral Letter of Credit Facilites [Member] | ||
| Line of Credit Facility [Line Items] | ||
| Outstanding letters of credit | $ 396,000,000 | $ 394,000,000 |
| Bilateral letter of credit facilities, total available amount | 470,000,000 | 518,000,000 |
| Bilateral letter of credit facilities, collateral | 397,000,000 | 396,000,000 |
| Uncommitted Bilateral Letter of Credit Facilities [Member] | ||
| Line of Credit Facility [Line Items] | ||
| Outstanding letters of credit | 100,000,000 | 158,000,000 |
| Bilateral letter of credit facilities, collateral | $ 100,000,000 | $ 100,000,000 |