Basis of Presentation - Statements of Operations Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Revenue
Revenue from Sales	$ 1,020	$ 1,052
Production Expense
Lease Operating Expense	138	151
Production and Ad Valorem Taxes	39	49
Gathering, Transportation and Processing Expense	95	102
Total	276	305
Exploration Expense
Leasehold Impairment	1,485	0
Seismic, Geological and Geophysical	4	5
Staff Expense	13	12
Other	2	7
Total	1,504	24
Other Operating Expense, Net
Finance Lease Right-of-Use Asset Impairment	40	0
Firm Transportation Exit Cost	0	92
Other, Net	4	25
Total	44	117
Other Revenue
Other Revenue
Revenue from Sales	1	41
(Loss) Income from Equity Method Investments and Other
Other Revenue
Revenue from Sales	(24)	17
Midstream Services Revenues – Third Party
Other Revenue
Revenue from Sales	25	24
Other Royalty Expense
Production Expense
Cost of Purchased Oil and Gas	4	$ 3
Exploration Expense
Total	$ 1,504