INVESTMENTS AND RELATED-PARTY TRANSACTIONS (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) interest	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Equity Method Investments
Equity method investment amounts	$ 1,680	$ 1,515	$ 1,401
Equity investments dividends paid	329	297	224
Excess of investments in equity investees over the underlying equity in net assets	636
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 and other income	1,932	1,252	1,238
Costs and expenses	1,527	973	1,043
Net income	405	279	195
Equity-method investments financial information summarized by Balance Sheet line item
Current assets	547	602
Non-current assets	2,139	2,072
Current liabilities	237	247
Long-term debt	1,042	1,174
Other non-current liabilities	22	66
Stockholders’ equity	1,385	1,187
RELATED-PARTY TRANSACTIONS
Sales	805	636	602
Purchases	502	387	7
Services	52	38	17
Advances and amounts due from	63	63	59
Amounts due to	$ 46	$ 45	$ 0
General Partner of Plains All American Pipeline, L.P
Equity Method Investments
Ownership interest (as a percent)	11.00%
RELATED-PARTY TRANSACTIONS
Sales to related party (as a percent)	89.00%	86.00%	89.00%
Plains All American Pipeline, LP
Equity Method Investments
Ownership interest (as a percent)	40.00%
Dolphin Energy
Equity Method Investments
Ownership interest (as a percent)	24.50%
Number of separate economic interests comprising investment in unconsolidated affiliate | interest	2
Equity method investment ownership percentage	24.50%
OxyChem Ingleside facility
Equity Method Investments
Ownership interest (as a percent)	50.00%
Ingleside ethylene
RELATED-PARTY TRANSACTIONS
Purchases from related party (as a percent)	98.00%