v3.22.4
Pensions and Other Postretirement Benefits (Rollforward of Fair Value of Investments Classified as Level 3) (Details) - Pension Plan [Member] - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year $ 20,416 $ 19,723
Fair value of plan assets at end of year 16,589 20,416
Real estate [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 370  
Fair value of plan assets at end of year 404 370
Resource and royalties [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 978  
Fair value of plan assets at end of year 1,198 978
Private Debt, Specialty Portfolio Strategy [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 16  
Fair value of plan assets at end of year 36 16
Public Equity Investment, Specialty Portfolio Strategy [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 0  
Fair value of plan assets at end of year 5 0
Private Equity Funds, Specialty Portfolio Strategy [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 295  
Fair value of plan assets at end of year $ 304 295
Absolute Return Funds [Member] | Minimum [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Investment redemption, notice period 5 days  
Absolute Return Funds [Member] | Maximum [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Investment redemption, notice period 90 days  
Absolute Return, Specialty Portfolio Strategy [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year $ 39  
Fair value of plan assets at end of year 35 39
Alternative Risk Premia [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 239  
Fair value of plan assets at end of year $ 155 239
Alternative Risk Premia [Member] | Minimum [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Investment redemption, notice period 5 days  
Alternative Risk Premia [Member] | Maximum [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Investment redemption, notice period 60 days  
Bond Forwards [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year $ 64  
Fair value of plan assets at end of year (23) 64
Bond, Options [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 0  
Fair value of plan assets at end of year 1 0
Credit Default Swap [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year (2)  
Fair value of plan assets at end of year (1) (2)
Swap [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year (1)  
Fair value of plan assets at end of year (1) (1)
Emerging Market Debt, Swap [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 0  
Fair value of plan assets at end of year 2 0
Emerging Market Debt, Foreign Exchange Forward [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 4  
Fair value of plan assets at end of year 0 4
Public Equities, Foreign Exchange Forwards [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year (5)  
Fair value of plan assets at end of year (16) (5)
Public Equities, Swap [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 10  
Fair value of plan assets at end of year (57) 10
Private Equities, Foreign Exchange Forwards [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 0  
Fair value of plan assets at end of year (1) 0
Resource And Royalties, Commodity Swaps [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year (30)  
Fair value of plan assets at end of year (44) (30)
Infrastructure, Foreign Exchange Forwards [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 1  
Fair value of plan assets at end of year 1 1
Absolute Return Funds, Foreign Exchange Forwards [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 0  
Fair value of plan assets at end of year 3 0
Absolute Return Funds, Options [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 74  
Fair value of plan assets at end of year 70 74
Other - Operating assets, at cost [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 134  
Fair value of plan assets at end of year 155 134
Other - Operating liabilities, at cost [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 47  
Fair value of plan assets at end of year 42 47
Level 3 [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 949 783
Actual return relating to assets still held at the reporting date 198 178
Purchases 2 6
Disbursements (59) (18)
Fair value of plan assets at end of year 1,090 949
Level 3 [Member] | Real estate [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 272 279
Actual return relating to assets still held at the reporting date (23) (13)
Purchases 2 6
Disbursements (2) 0
Fair value of plan assets at end of year 249 272
Level 3 [Member] | Resource and royalties [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 677 504
Actual return relating to assets still held at the reporting date 221 191
Purchases 0 0
Disbursements (57) (18)
Fair value of plan assets at end of year $ 841 $ 677