SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) (Schedule of Standardized Measure of Future Net Cash Flows) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Future cash inflows		$ 345	$ 10,536
Future production expense		(175)	(4,768)
Future development costs		(439)	(4,130)
Future income tax expense		0	0
Future net cash flows		(269)	1,638
Discounted at 10% per year		32	(246)
Standardized Measure		(237)	1,392	$ 6,421
Asset Retirement Obligation	$ 2,580	2,635	2,771	$ 2,744
United States oil and gas operations
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Asset Retirement Obligation		$ 400	$ 1,900