Disclosures About Fair Value Measurements (Assets And Liabilities That Are Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	$ 85	$ 82
Investment in affiliate	187	172
Contingent consideration	91
Total assets	395	306
Total recurring fair value measurements	375	279
Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	32	52
Commodity derivatives	20	27
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	85	82
Investment in affiliate	187	0
Contingent consideration	0
Total assets	272	82
Total recurring fair value measurements	272	82
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
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
Investment in affiliate	0	172
Contingent consideration	91
Total assets	123	224
Total recurring fair value measurements	103	197
Significant Other Observable Inputs (Level 2) | Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivatives	32	52
Commodity derivatives	20	27
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	0	0
Investment in affiliate	0	0
Contingent consideration	0
Total assets	0	0
Total recurring fair value measurements	0	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