Basis of Presentation - Statements of Operations Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Other Revenue
Revenue from Sales	$ 1,052	$ 1,286
Production Expense
Lease Operating Expense	151	155
Production and Ad Valorem Taxes	49	54
Gathering, Transportation and Processing Expense	102	93
Total	305	319
Other Operating Expense, Net
Exploration Expense	24	35
Other, Net	25	15
Total	49	50
Other Revenue
Other Revenue
Revenue from Sales	41	60
Income from Equity Method Investees
Other Revenue
Revenue from Sales	17	47
Midstream Services Revenues – Third Party
Other Revenue
Revenue from Sales	24	13
Other Royalty Expense
Production Expense
Costs and Expenses	$ 3	$ 17