The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Goodwill) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) $ / bbl	Dec. 31, 2013 USD ($) $ / bbl
Goodwill [Line Items]
Goodwill, acquired during the period				$ 1,900
Goodwill [Roll Forward]
Goodwill, beginning balance		$ 0	$ 1,916
Purchase accounting adjustments			22
Disposal of Eagle Ford shale assets (see Note 2)			(221)
Impairment charge	$ 0	$ 0	(1,717)
Goodwill, ending balance			$ 0	$ 1,916
Oil \| Minimum
Goodwill [Roll Forward]
Average sales price (usd per bbl) \| $ / bbl			62	90
Oil \| Maximum
Goodwill [Roll Forward]
Average sales price (usd per bbl) \| $ / bbl			80	98