INVESTMENTS AND RELATED-PARTY TRANSACTIONS (Details) shares in Millions, $ in Millions		1 Months Ended		12 Months Ended
	Mar. 24, 2016 shares	Oct. 31, 2014 USD ($)	Oct. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) item shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
RELATED-PARTY TRANSACTIONS
Sales to related parties				$ 555	$ 835	$ 663
Purchases from related parties				26	6
Services to related parties				32	27	30
Advances and amounts due from related parties				60	26	67
Amounts due to related parties				5	15	3
Equity Method Investments
Equity method investment amounts				1,267	1,171	1,459
Equity investments dividends paid				438	396	447
Excess of investments in equity investees over the underlying equity in net assets				625
Excess of investments in equity investees over the underlying equity in net assets, which represents goodwill				542
Equity-method investments financial information summarized by Income Statement line item
Revenues				1,050	3,090	3,373
Costs and expenses				827	2,774	2,987
Net income				223	316	$ 386
Equity-method investments financial information summarized by Balance Sheet line item
Current assets				896	1,127
Non-current assets				3,589	2,925
Current liabilities				536	771
Long-term debt				2,141	1,701
Other non-current liabilities				148	83
Stockholders' equity				$ 1,659	$ 1,498
General Partner of Plains All American Pipeline,L.P
EQUITY INVESTMENTS
Ownership interest (as a percent)				13.00%
Proceeds from sale		$ 1,700	$ 1,400
Pre-tax gain on sale of investments		$ 1,400	$ 1,000
RELATED-PARTY TRANSACTIONS
Sales to related party (as a percent)				87.00%	46.00%	72.00%
California Resource Corporation
EQUITY INVESTMENTS
Interest in investment recorded as available for sale asset (as a percent)				18.70%
Stock dividend declared (in shares) | shares				71.5
Other than temporary loss				$ 227
Available for sale investment				$ 167	$ 394
California Resource Corporation | Stock dividend distribution
EQUITY INVESTMENTS
Stock dividend, shares distributed | shares	71.5
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