Accounts Receivable (Schedule Of Components Of Accounts Receivable) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Joint interest billings	$ 104	$ 110
Other	67	69
Gross accounts receivable	1,338	1,374
Allowance for doubtful accounts	(18)	(18)
Net accounts receivable	1,320	1,356
Oil, Gas And NGL Sales [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	495	487
Marketing And Midstream Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 672	$ 708