Fair Value Measurements (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets:
Deferred compensation plan assets	$ 89	$ 82
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	347	172
Total assets	466	306
Liabilities:
Total liabilities	22	27
Total recurring fair value measurements	444	279
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Deferred compensation plan assets	89	82
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	0	0
Total assets	89	82
Liabilities:
Total liabilities	0	0
Total recurring fair value measurements	89	82
Significant Other Observable Inputs (Level 2)
Assets:
Deferred compensation plan assets	0	0
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	347	172
Total assets	377	224
Liabilities:
Total liabilities	22	27
Total recurring fair value measurements	355	197
Significant Unobservable Inputs (Level 3)
Assets:
Deferred compensation plan assets	0	0
Investments in Affiliates, Subsidiaries, Associates, and Joint Ventures, Fair Value Disclosure	0	0
Total assets	0	0
Liabilities:
Total liabilities	0	0
Total recurring fair value measurements	0	0
Commodity derivatives
Assets:
Derivative assets	30	52
Liabilities:
Commodity derivatives	22	27
Commodity derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative assets	0	0
Liabilities:
Commodity derivatives	0	0
Commodity derivatives | Significant Other Observable Inputs (Level 2)
Assets:
Derivative assets	30	52
Liabilities:
Commodity derivatives	22	27
Commodity derivatives | Significant Unobservable Inputs (Level 3)
Assets:
Derivative assets	0	0
Liabilities:
Commodity derivatives	$ 0	$ 0