v3.21.1
Fair Value Measurement - FV Hierarchy (Details) - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in debt securities $ 552 $ 518
Commodity derivative asset, gross 278 255
Commodity derivative liability, gross 254 220
Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment in Equity Securities 1,564 1,256
Investments in debt securities 552 518
Commodity derivative asset, gross 278 255
Total assets 2,394 2,029
Commodity derivative liability, gross 254 220
Total liabilities 254 220
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment in Equity Securities 1,564 1,256
Investments in debt securities 10 17
Commodity derivative asset, gross 162 142
Total assets 1,736 1,415
Commodity derivative liability, gross 155 120
Total liabilities 155 120
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment in Equity Securities 0 0
Investments in debt securities 542 501
Commodity derivative asset, gross 104 101
Total assets 646 602
Commodity derivative liability, gross 89 91
Total liabilities 89 91
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment in Equity Securities 0 0
Investments in debt securities   0
Commodity derivative asset, gross 12 12
Total assets 12 12
Commodity derivative liability, gross 10 9
Total liabilities $ 10 $ 9