Basis of Presentation - Statements of Operations Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Revenue
Revenue from Sales	$ 1,093	$ 1,230	$ 2,145	$ 2,516
Production Expense
Lease Operating Expense	122	132	273	287
Production and Ad Valorem Taxes	41	50	90	104
Gathering, Transportation and Processing Expense	96	98	198	191
Total	260	290	565	609
Other Operating Expense, Net
Exploration Expense	33	29	57	64
Marketing Expense	14	9	19	16
Other, Net	8	(4)	28	4
Total	55	34	104	84
Other Revenue
Other Revenue
Revenue from Sales	36	64	77	124
Income from Equity Method Investees and Other
Other Revenue
Revenue from Sales	16	49	33	96
Midstream Services Revenues – Third Party
Other Revenue
Revenue from Sales	20	15	44	28
Other Royalty Expense
Production Expense
Cost of Purchased Oil and Gas	$ 1	$ 10	$ 4	$ 27