revenue from contracts with customers - Revenues (Details) - Minimum - CAD ($) $ in Millions |
Jun. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Disclosure of transaction price allocated to remaining performance obligations | ||
| Transaction price allocated to remaining performance obligations | $ 3,307 | $ 3,263 |
| The twelve month period ending one year hence | ||
| Disclosure of transaction price allocated to remaining performance obligations | ||
| Transaction price allocated to remaining performance obligations | 2,390 | 2,306 |
| The twelve month period ending two years hence | ||
| Disclosure of transaction price allocated to remaining performance obligations | ||
| Transaction price allocated to remaining performance obligations | 888 | 933 |
| Thereafter | ||
| Disclosure of transaction price allocated to remaining performance obligations | ||
| Transaction price allocated to remaining performance obligations | $ 29 | $ 24 |