Changes in Accumulated Other Comprehensive Loss ("AOCL") by Component - Amounts in Pension and Post-retirement Defined Benefit Plans Reclassified from AOCL (Details) - Reclassification out of Accumulated Other Comprehensive Income - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Recognition of net actuarial loss	$ 39	$ 53	$ 116	$ 158
Income tax recovery	(9)	(14)	(27)	(41)
Total net of income tax	$ 30	$ 39	$ 89	$ 117