Basis of Presentation - Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Accounts Receivable, Net
Commodity Sales	$ 405	$ 383
Joint Interest Billings	177	137
Other	103	111
Allowance for Doubtful Accounts	(8)	(15)
Total	677	616
Other Current Assets
Commodity Derivative Assets	90	180
Inventories, Materials and Supplies	74	55
Assets Held for Sale	0	133
Prepaid Expenses and Other Current Assets	113	50
Total	277	418
Other Noncurrent Assets
Equity Method Investments	959	286
Operating Lease Right of Use Assets	275	0
Customer-Related Intangible Assets, Net	286	310
Goodwill	110	110
Other Assets, Noncurrent	150	135
Total	1,780	841
Other Current Liabilities
Production and Ad Valorem Taxes	147	103
Asset Retirement Obligations	89	118
Interest Payable	87	66
Operating Lease Liabilities	97	0
Commercial Paper Borrowings	511	0
Other Liabilities, Current	259	232
Total	1,190	519
Other Noncurrent Liabilities
Deferred Compensation Liabilities	148	147
Asset Retirement Obligations	699	762
Operating Lease Liabilities	209	0
Firm Transportation Exit Cost Accrual	133	67
Other Liabilities, Noncurrent	149	189
Total	1,338	1,165
Accumulated amortization	$ 54	$ 30