Derivative Financial Instruments (Schedule Of Derivative Financial Instruments Included In The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivatives Fair Value [Line Items]
Fair value of derivative assets	$ 212	$ 11
Fair value of derivative liabilities	358	244
Other Current Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative liabilities	331	187
Commodity Derivatives [Member] \| Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative assets	209	9
Commodity Derivatives [Member] \| Other Long-Term Assets [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative assets	2	1
Commodity Derivatives [Member] \| Other Current Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative liabilities	267	187
Commodity Derivatives [Member] \| Other Long-Term Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative liabilities	27	16
Interest Rate Derivatives [Member] \| Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative assets	1	1
Interest Rate Derivatives [Member] \| Other Current Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative liabilities	$ 64
Interest Rate Derivatives [Member] \| Other Long-Term Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair value of derivative liabilities		$ 41

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

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Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

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