INVESTMENTS AND RELATED-PARTY TRANSACTIONS (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Equity Method Investments
Equity method investment amounts	$ 1,515	$ 1,401	$ 1,267
Equity investments dividends paid	297	224	438
Excess of investments in equity investees over the underlying equity in net assets	649
Excess of investments in equity investees over the underlying equity in net assets, which represents goodwill	464
Equity-method investments financial information summarized by Income Statement line item
Revenues	1,252	1,238	1,050
Costs and expenses	973	1,043	827
Net income	279	195	223
Equity-method investments financial information summarized by Balance Sheet line item
Current assets	602	914
Non-current assets	2,072	3,605
Current liabilities	247	577
Long-term debt	1,174	1,957
Other non-current liabilities	66	159
Stockholders' equity	1,187	1,826
RELATED-PARTY TRANSACTIONS
Sales	636	602	555
Purchases	387	7	26
Services	38	17	32
Advances and amounts due from	63	$ 59	60
Amounts due to	$ 45		$ 5
General Partner of Plains All American Pipeline, L.P
RELATED-PARTY TRANSACTIONS
Sales to related party (as a percent)	86.00%	89.00%	87.00%
Ingleside ethylene
RELATED-PARTY TRANSACTIONS
Purchases from related party (as a percent)	98.00%
OxyChem Ingleside facility
EQUITY INVESTMENTS
Ownership interest (as a percent)	50.00%
Dolphin Energy
EQUITY INVESTMENTS
Equity method investment ownership percentage	24.50%
Ownership interest (as a percent)	24.50%
Number of separate economic interests comprising investment in unconsolidated affiliate | item	2