Environmental Liabilities and Expenditures (Details)	1 Months Ended	3 Months Ended
	Mar. 31, 2016 mi	Mar. 31, 2021 USD ($) site	Sep. 30, 2016 USD ($)	Dec. 31, 2020 USD ($)
Environmental remediation reserves
Number of Sites | site		168
Environmental remediation reserves, current, included in accrued liabilities		$ 1,152,000,000
Environmental remediation reserves, non-current, included in deferred credits and other liabilities - other		1,029,000,000		$ 1,028,000,000
Environmental reserves, exceeding $ ten million, threshold value		$ 10,000,000
Environmental reserves, exceeding $ ten million, number of sites | site		19
Environmental reserves, range between zero to $ one million site category, number of sites | site		96
Percent of reserve to be funded over the next three to four years		45.00%
Period of expending remaining environmental reserves (or more)		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 first half 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 first half of environmental reserves		4 years
NPL sites
Environmental remediation reserves
Number of Sites | site		34
Environmental remediation reserves, current, included in accrued liabilities		$ 445,000,000
Third-party sites
Environmental remediation reserves
Number of Sites | site		69
Environmental remediation reserves, current, included in accrued liabilities		$ 303,000,000
Occidental-operated sites
Environmental remediation reserves
Number of Sites | site		17
Environmental remediation reserves, current, included in accrued liabilities		$ 141,000,000
Closed or non-operated Occidental sites
Environmental remediation reserves
Number of Sites | site		48
Environmental remediation reserves, current, included in accrued liabilities		$ 263,000,000
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
Accrued liabilities
Environmental remediation reserves
Environmental remediation reserves, current, included in accrued liabilities		123,000,000
Deferred credits and other liabilities - other
Environmental remediation reserves
Environmental remediation reserves, non-current, included in deferred credits and other liabilities - other		$ 1,000,000,000.0