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SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) (Schedule of Capitalized Costs) (Details)
$ in Millions
3 Months Ended 12 Months Ended
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
$ / Boe
Dec. 31, 2015
USD ($)
$ / Boe
Oil and Gas Exploration and Production Industries Disclosures [Abstract]            
Properties subject to amortization         $ 27,507 $ 24,538
Accumulated amortizationa         (27,433) (22,276)
Total         74 2,262
Impairment of Oil and Gas Properties $ 200 $ 300 $ 3,800 $ 0 $ 4,317 $ 13,144
Average Depletion Depreciation and Amortization Expense Per Unit of Production | $ / Boe         17.58 33.46