ENVIRONMENTAL LIABILITIES AND EXPENDITURES (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2016 mi	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) category site	Dec. 31, 2016 USD ($) site	Dec. 31, 2015 USD ($) site
Environmental remediation reserves
Number of Sites | site			148	147	149
Environmental remediation reserves, current, included in accrued liabilities			$ 137	$ 131	$ 70
Environmental remediation reserves, noncurrent, included in deferred credits and other liabilities - other			$ 728	739	316
Number of non-NPL sites categories | category			3
Reserve Balance			$ 865	870	386
Environmental reserves, exceeding $ ten million, threshold value			$ 10
Environmental reserves, exceeding $ ten million, number of sites | site			16
Environmental reserves, range between zero to $ one million site category, number of sites | site			89
Percent of reserve to be funded over the next three to four years			40.00%
Minimum period of expending second half of environmental reserves			10 years
Environmental remediation additional loss range			$ 1,100
Environmental costs, including certain estimates by segment
Operating Expenses			161	151	180
Capital Expenditures			101	73	167
Low end of range
Environmental remediation reserves
Environmental reserves, range between zero to $ one million site category			$ 0
Period of expending 40 percent of environmental reserves			3 years
High end of range
Environmental remediation reserves
Environmental reserves, range between zero to $ one million site category			$ 1
Period of expending 40 percent of environmental reserves			4 years
Oil and Gas
Environmental costs, including certain estimates by segment
Operating Expenses			$ 68	65	93
Capital Expenditures			77	43	122
Chemical
Environmental costs, including certain estimates by segment
Operating Expenses			78	75	74
Capital Expenditures			18	25	41
Midstream and Marketing
Environmental costs, including certain estimates by segment
Operating Expenses			15	11	13
Capital Expenditures			6	5	4
Corporate
Environmental costs, including certain estimates by segment
Remediation Expenses			$ 39	$ 61	$ 117
Lower Passaic River
Environmental remediation reserves
Stretch of Lower Passaic river requiring remedial actions | mi	8.3
Stretch of Lower Passaic river not covered by remedial actions | mi	9
Clean-up estimated cost		$ 165
NPL sites
Environmental remediation reserves
Number of Sites | site			34	33	34
Reserve Balance			$ 457	$ 461	$ 27
Number of sites with significant environmental remediation reserves | site			3
Percentage of environmental reserves accounted for by associated sites			95.00%
Number of sites indemnified by third party | site			17
Third-party sites
Environmental remediation reserves
Number of Sites | site			70	68	66
Reserve Balance			$ 157	$ 163	$ 128
Number of sites with significant environmental remediation reserves | site			5
Percentage of environmental reserves accounted for by associated sites			60.00%
Number of sites indemnified by third party | site			9
Number of sites not indemnified by third party | site			70
Occidental-operated sites
Environmental remediation reserves
Number of Sites | site			15	17	18
Reserve Balance			$ 108	$ 106	$ 107
Number of sites with significant environmental remediation reserves | site			3
Percentage of environmental reserves accounted for by associated sites			49.00%
Closed or non-operated Occidental sites
Environmental remediation reserves
Number of Sites | site			29	29	31
Reserve Balance			$ 143	$ 140	$ 124
Number of sites with significant environmental remediation reserves | site			5
Percentage of environmental reserves accounted for by associated sites			62.00%