SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) shares in Millions, $ in Millions			12 Months Ended
	Feb. 18, 2026 shares	Oct. 01, 2025 USD ($)	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 USD ($)
Summary of Significant Accounting Policies [Line Items]
Number of reportable segments | segment			2
Non-voting limited partner interest			2.00%
Investments in unconsolidated entities			$ 2,475	$ 2,646
Noncontrolling interest			564	321
Assets			84,186	85,445
Net sales			21,569	22,710	$ 23,230
Trade receivables			2,575	2,839
Net capitalized costs attributable to unproved properties			7,700	$ 10,200
Goodwill			$ 668
Minimum period of investigations and cleanup for CERCLA sites			10 years
Carbon Engineering, Ltd.
Summary of Significant Accounting Policies [Line Items]
Other intangible assets			$ 954
Crownrock L.P.
Summary of Significant Accounting Policies [Line Items]
Issuance of shares upon approval (in shares) | shares				29.6
Land
Summary of Significant Accounting Policies [Line Items]
Impairment and related charges				$ 334	180
Low end of range
Summary of Significant Accounting Policies [Line Items]
Amortization period (in years)			9 years
Low end of range | Midstream and marketing
Summary of Significant Accounting Policies [Line Items]
The estimated useful lives of occidental's chemical assets			3 years
High end of range
Summary of Significant Accounting Policies [Line Items]
Amortization period (in years)			25 years
High end of range | Midstream and marketing
Summary of Significant Accounting Policies [Line Items]
The estimated useful lives of occidental's chemical assets			40 years
Outside North America
Summary of Significant Accounting Policies [Line Items]
Assets			$ 7,800
Net sales			4,200
Disposed of by sale | OxyChem
Summary of Significant Accounting Policies [Line Items]
Proceeds received for divested assets		$ 9,700
VIE's
Summary of Significant Accounting Policies [Line Items]
Construction in progress			1,200
BlackRock, Inc.
Summary of Significant Accounting Policies [Line Items]
Investments in unconsolidated entities			500
Equity method investment commitments			$ 550
WES
Summary of Significant Accounting Policies [Line Items]
Limited partner interest			40.60%
Minority interest in new venture			43.10%
Investments in unconsolidated entities			$ 2,032
WES | Subsequent event
Summary of Significant Accounting Policies [Line Items]
Limited partner interest	40.90%
Black Butte Coal Company
Summary of Significant Accounting Policies [Line Items]
Impairment of equity method investment					$ 29
WES
Summary of Significant Accounting Policies [Line Items]
Non-voting general partner interest			2.20%
WES | Subsequent event
Summary of Significant Accounting Policies [Line Items]
Limited partnership number of shares transferred (in shares) | shares	15.3