Disclosures About Fair Value Measurements (Assets And Liabilities That Are Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	$ 72	$ 85
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	123	187
Total assets	203	416
Financial and Nonfinancial Liabilities, Fair Value Disclosure	300
Total recurring fair value measurements	(97)	396
Contingent Consideration Classified as Assets, Fair Value Disclosure		91
Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	8	32
Commodity derivatives	209	20
Marketing derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives		21
Commodity derivatives	91
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	72	85
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	123	187
Total assets	195	272
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0
Total recurring fair value measurements	195	272
Contingent Consideration Classified as Assets, Fair Value Disclosure		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	0	0
Commodity derivatives	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Marketing derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives		0
Commodity derivatives	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	0	0
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	0	0
Total assets	8	123
Financial and Nonfinancial Liabilities, Fair Value Disclosure	209
Total recurring fair value measurements	(201)	103
Contingent Consideration Classified as Assets, Fair Value Disclosure		91
Significant Other Observable Inputs (Level 2) | Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	8	32
Commodity derivatives	209	20
Significant Other Observable Inputs (Level 2) | Marketing derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives		0
Commodity derivatives	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	0	0
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	0	0
Total assets	0	21
Financial and Nonfinancial Liabilities, Fair Value Disclosure	91
Total recurring fair value measurements	(91)	21
Contingent Consideration Classified as Assets, Fair Value Disclosure		0
Significant Unobservable Inputs (Level 3) | Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	0	0
Commodity derivatives	0	$ 0
Significant Unobservable Inputs (Level 3) | Marketing derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	$ 91