ENVIRONMENTAL LIABILITIES AND EXPENDITURES (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2016 mi	Sep. 30, 2016 USD ($)	Dec. 31, 2018 USD ($) site category	Dec. 31, 2017 USD ($) site	Dec. 31, 2016 USD ($) site
Environmental remediation reserves
Number of Sites | site			145	148	147
Environmental remediation reserves, current, included in accrued liabilities			$ 120,000,000	$ 137,000,000	$ 131,000,000
Environmental remediation reserves, noncurrent, included in deferred credits and other liabilities - other			$ 762,000,000	728,000,000	739,000,000
Number of non-NPL sites categories | category			3
Reserve Balance			$ 882,000,000	865,000,000	870,000,000
Environmental reserves, exceeding $ ten million, threshold value			$ 10,000,000
Environmental reserves, exceeding $ ten million, number of sites | site			16
Environmental reserves, range between zero to $ one million site category, number of sites | site			87
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			$ 1,100,000,000
Environmental costs, including certain estimates by segment
Operating Expenses			190,000,000	161,000,000	151,000,000
Capital Expenditures			103,000,000	101,000,000	73,000,000
Oil and Gas
Environmental costs, including certain estimates by segment
Operating Expenses			95,000,000	68,000,000	65,000,000
Capital Expenditures			75,000,000	77,000,000	43,000,000
Chemical
Environmental costs, including certain estimates by segment
Operating Expenses			80,000,000	78,000,000	75,000,000
Capital Expenditures			23,000,000	18,000,000	25,000,000
Midstream and Marketing
Environmental costs, including certain estimates by segment
Operating Expenses			15,000,000	15,000,000	11,000,000
Capital Expenditures			5,000,000	6,000,000	5,000,000
Corporate
Environmental costs, including certain estimates by segment
Remediation Expenses			$ 47,000,000	$ 39,000,000	$ 61,000,000
NPL sites
Environmental remediation reserves
Number of Sites | site			34	34	33
Reserve Balance			$ 458,000,000	$ 457,000,000	$ 461,000,000
Number of sites with significant environmental remediation reserves | site			4
Percentage of environmental reserves accounted for by associated sites			94.00%
Number of sites indemnified by third party | site			17
Third-party sites
Environmental remediation reserves
Number of Sites | site			68	70	68
Reserve Balance			$ 168,000,000	$ 157,000,000	$ 163,000,000
Number of sites with significant environmental remediation reserves | site			5
Percentage of environmental reserves accounted for by associated sites			62.00%
Number of sites indemnified by third party | site			9
Number of sites not indemnified by third party | site			68
Occidental-operated sites
Environmental remediation reserves
Number of Sites | site			14	15	17
Reserve Balance			$ 115,000,000	$ 108,000,000	$ 106,000,000
Number of sites with significant environmental remediation reserves | site			3
Percentage of environmental reserves accounted for by associated sites			64.00%
Closed or non-operated Occidental sites
Environmental remediation reserves
Number of Sites | site			29	29	29
Reserve Balance			$ 141,000,000	$ 143,000,000	$ 140,000,000
Number of sites with significant environmental remediation reserves | site			4
Percentage of environmental reserves accounted for by associated sites			61.00%
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		$ 165,000,000
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			$ 1,000,000
Period of expending 40 percent of environmental reserves			4 years