Basis of Presentation - Statements of Operations Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Revenue
Revenue from Sales	$ 1,119	$ 1,273	$ 3,264	$ 3,789
Production Expense
Lease Operating Expense	132	124	405	411
Production and Ad Valorem Taxes	52	47	142	151
Gathering, Transportation and Processing Expense	108	97	306	292
Total	297	273	862	886
Other Operating Expense, Net
Exploration Expense	25	25	82	89
Marketing Expense	7	11	26	21
Firm Transportation Exit Cost	0	0	92	0
Other, Net	29	(9)	57	(3)
Total	61	27	257	107
Other Revenue
Other Revenue
Revenue from Sales	29	65	106	189
Income from Equity Method Investments and Other
Other Revenue
Revenue from Sales	10	44	43	140
Midstream Services Revenues – Third Party
Other Revenue
Revenue from Sales	19	21	63	49
Other Royalty Expense
Production Expense
Cost of Purchased Oil and Gas	$ 5	$ 5	$ 9	$ 32