ENVIRONMENTAL LIABILITIES AND EXPENDITURES (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2016 mi	Sep. 30, 2016 USD ($)	Dec. 31, 2020 USD ($) site	Dec. 31, 2019 USD ($) site	Dec. 31, 2018 USD ($)
Environmental remediation reserves
Number of sites			170	177
Environmental remediation reserves, current, included in accrued liabilities | $			$ 123,000,000	$ 162,000,000
Environmental remediation reserves, noncurrent, included in deferred credits and other liabilities - other | $			1,028,000,000	1,035,000,000
Remediation balance | $			1,151,000,000	1,197,000,000
Environmental reserves, exceeding $ ten million, threshold value | $			$ 10,000,000
Environmental reserves, exceeding $ ten million, number of sites			19
Environmental reserves, range between zero to $ one million site category, number of sites			96
Remediation Expenses | $			$ 36,000,000	$ 112,000,000	$ 47,000,000
Percent of reserve to be funded over the next three to four years			45.00%
Minimum period of expending second half of environmental reserves			10 years
Environmental remediation additional loss range | $			$ 1,100,000,000
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
NPL sites
Environmental remediation reserves
Number of sites			35	36
Remediation balance | $			$ 447,000,000	$ 463,000,000
Number of sites with significant environmental remediation reserves			5
Percentage of environmental reserves accounted for by associated sites			92.00%
Number of sites indemnified by third party			17
Third-party sites
Environmental remediation reserves
Number of sites			69	74
Remediation balance | $			$ 293,000,000	$ 311,000,000
Number of sites with significant environmental remediation reserves			7
Percentage of environmental reserves accounted for by associated sites			76.00%
Number of sites indemnified by third party			69
Number of sites not indemnified by third party			69
Occidental-operated sites
Environmental remediation reserves
Number of sites			17	17
Remediation balance | $			$ 144,000,000	$ 154,000,000
Number of sites with significant environmental remediation reserves			2
Percentage of environmental reserves accounted for by associated sites			70.00%
Closed or non-operated Occidental sites
Environmental remediation reserves
Number of sites			49	50
Remediation balance | $			$ 267,000,000	$ 269,000,000
Number of sites with significant environmental remediation reserves			5
Percentage of environmental reserves accounted for by associated sites			70.00%
Maxus
Environmental remediation reserves
Number of sites indemnified by third party			9
Passaic River
Environmental remediation reserves
Stretch of Lower Passaic river requiring remedial actions | mi	8.3
River stretch which may require remedial actions | mi	9
Clean-up estimated cost | $		$ 165,000,000