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SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) (Schedule of Changes in the Standardized Measure) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves [Roll Forward]    
Balance at beginning of year $ 1,392 $ 6,421
Sales, net of production expenses (831) (928)
Net changes in sales and transfer prices, net of production expenses (341) (7,766)
Extensions, discoveries and improved recoveries 0 45
Changes in estimated future development costs, including timing and other 146 1,287
Previously estimated development costs incurred during the year 295 985
Sales of reserves in-place (1,049) 0
Revisions of quantity estimates 12 (1,170)
Accretion of discount 139 797
Net change in income taxes 0 1,721
Total changes (1,629) (5,029)
Balance at end of year $ (237) $ 1,392