Pension and Other Benefits - Net Periodic Benefit Cost for DB Pension Plans and Other Benefits (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan and Other Postretirement Benefit Plans
Total other components of net periodic benefit (recovery) cost	$ (102)	$ (95)	$ (304)	$ (286)
Defined Benefit Pension Plan
Defined Benefit Plan and Other Postretirement Benefit Plans
Current service cost (benefits earned by employees)	37	42	111	128
Interest cost on benefit obligation	95	88	287	264
Expected return on fund assets	(240)	(240)	(719)	(720)
Recognized net actuarial loss	39	52	115	155
Total other components of net periodic benefit (recovery) cost	(106)	(100)	(317)	(301)
Net periodic benefit (recovery) cost	(69)	(58)	(206)	(173)
Other Post-retirement Benefit Plans
Defined Benefit Plan and Other Postretirement Benefit Plans
Current service cost (benefits earned by employees)	3	4	8	10
Interest cost on benefit obligation	4	4	12	12
Expected return on fund assets	0	0	0	0
Recognized net actuarial loss	0	1	1	3
Total other components of net periodic benefit (recovery) cost	4	5	13	15
Net periodic benefit (recovery) cost	$ 7	$ 9	$ 21	$ 25