Accounts Receivable (Schedule Of Components Of Accounts Receivable) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Joint interest billings	$ 161	$ 150
Other	28	15
Gross accounts receivable	793	862
Allowance for doubtful accounts	(6)	(7)
Net accounts receivable	787	855
Oil, Gas and NGL Sales [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	396	413
Marketing Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 208	$ 284