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RESERVE ROLLFORWARDS (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Movement In Valuation Allowances And Reserves Roll Forward      
Beginning Balance $ 919 $ 945 $ 1,125
Charges (Credits) to Cost and Expense 163 (4) (94)
Charged to Other Accounts 11 5 (5)
Deductions 30 27 81
Ending Balance 1,063 919 945
Allowance for Doubtful Accounts [Member]      
Movement In Valuation Allowances And Reserves Roll Forward      
Beginning Balance 10 13 10
Charges (Credits) to Cost and Expense 3 (2) 1
Charged to Other Accounts 0 0 2
Deductions 1 1 0
Ending Balance 12 10 13
LIFO Inventory [Member]      
Movement In Valuation Allowances And Reserves Roll Forward      
Beginning Balance 264 296 462
Charges (Credits) to Cost and Expense 24 (32) (166)
Charged to Other Accounts 0 0 0
Deductions 0 0 0
Ending Balance 288 264 296
Non-environmental asset retirement obligation Costs [Member]      
Movement In Valuation Allowances And Reserves Roll Forward      
Beginning Balance 46 46 44
Charges (Credits) to Cost and Expense 2 0 4
Charged to Other Accounts 1 0 0
Deductions 0 0 2
Ending Balance 49 46 46
Environmental Contingencies [Member]      
Movement In Valuation Allowances And Reserves Roll Forward      
Beginning Balance 321 336 345
Charges (Credits) to Cost and Expense 8 10 9
Charged to Other Accounts 4 1 11
Deductions 29 26 29
Ending Balance 304 321 336
Valuation Allowance of Deferred Tax Assets [Member]      
Movement In Valuation Allowances And Reserves Roll Forward      
Beginning Balance 278 254 264
Charges (Credits) to Cost and Expense 126 20 58
Charged to Other Accounts 6 4 (18)
Deductions 0 0 50
Ending Balance $ 410 $ 278 $ 254