v3.19.3.a.u2
Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Dec. 18, 2018
Financial Assets      
Investment in Cenovus Energy $ 2,111 $ 1,462  
Derivative Asset, Fair Value, Amount Offset Against Collateral 126 161  
Carrying Amount [Member]      
Financial Assets      
Investment in Cenovus Energy 2,111 1,462  
Available for sale debt securities at fair value 241   $ 0
Total loans and advances - related parties 339 468  
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]      
Total debt, excluding capital leases 14,175 14,191  
Carrying Amount [Member] | Commodity Contract [Member]      
Financial Assets      
Derivative Asset, Fair Value, Amount Offset Against Collateral 125 170  
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]      
Commodity derivatives 106 $ 110  
Fair Value [Member]      
Financial Assets      
Investment in Cenovus Energy 2,111   1,462
Available for sale debt securities at fair value 241   0
Total loans and advances - related parties 339   468
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]      
Total debt, excluding capital leases 18,108   16,147
Fair Value [Member] | Commodity Contract [Member]      
Financial Assets      
Derivative Asset, Fair Value, Amount Offset Against Collateral 125   170
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]      
Commodity derivatives $ 106   $ 110