XML 178 R133.htm IDEA: XBRL DOCUMENT v3.20.4
Pensions and Other Post-Employment Benefits - Summary of Defined Benefit and OPEB Plan Obligation and Funded Status (Detail) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Pension Benefits [Member]      
Disclosure Of Net Defined Benefit Liability Asset [Line Items]      
Current Service Costs $ 13 $ 11 $ 13
Interest Income (Costs) (3) (3) (3)
Re-measurements:      
(Gains) Losses From Experience Adjustments 1 (4)  
(Gains) Losses From Changes in Financial Assumptions 15 12  
Return on Plan Assets (Excluding Interest Income) 5 15 (7)
Pension and OPEB (Liability) (71) (51)  
Pension Benefits [Member] | Present value of defined benefit obligation [Member]      
Disclosure Of Net Defined Benefit Liability Asset [Line Items]      
Defined Benefit Obligation, Beginning of Year 158 167  
Current Service Costs 13 11  
Interest Income (Costs) 5 6  
Benefits Paid (6) (36)  
Plan Participant Contributions 2 2  
Re-measurements:      
(Gains) Losses From Experience Adjustments 1 (4)  
(Gains) Losses From Changes in Financial Assumptions 15 12  
Defined Benefit Obligation, End of Year 188 158 167
Pension Benefits [Member] | Plan assets [Member]      
Disclosure Of Net Defined Benefit Liability Asset [Line Items]      
Fair Value of Plan Assets, Beginning of Year 107 113  
Interest Income (Costs) 2 3  
Benefits Paid (5) (35)  
Employer Contributions 6 9  
Plan Participant Contributions 2 2  
Re-measurements:      
Return on Plan Assets (Excluding Interest Income) 5 15  
Fair Value of Plan Assets, End of Year 117 107 113
OPEB [Member]      
Disclosure Of Net Defined Benefit Liability Asset [Line Items]      
Current Service Costs 1 1 1
Interest Income (Costs)   (1) (1)
Re-measurements:      
(Gains) Losses From Experience Adjustments (2)    
(Gains) Losses From Changes in Financial Assumptions 1 1 (1)
Pension and OPEB (Liability) (20) (22)  
OPEB [Member] | Present value of defined benefit obligation [Member]      
Disclosure Of Net Defined Benefit Liability Asset [Line Items]      
Defined Benefit Obligation, Beginning of Year 22 21  
Current Service Costs 1 1  
Interest Income (Costs)   1  
Benefits Paid (2) (2)  
Re-measurements:      
(Gains) Losses From Experience Adjustments (2)    
(Gains) Losses From Changes in Financial Assumptions 1 1  
Defined Benefit Obligation, End of Year $ 20 $ 22 $ 21