Accounts Receivable (Schedule Of Components Of Accounts Receivable) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Joint interest billings	$ 152	$ 211
Other	62	30
Gross accounts receivable	1,041	1,123
Allowance for doubtful accounts	(18)	(18)
Net accounts receivable	1,023	1,105
Oil, Gas And NGL Sales [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	350	362
Marketing And Midstream Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 477	$ 520