SUPPLEMENTARY OIL AND GAS INFORMATION (UNAUDITED) (Schedule of Changes in the Standardized Measure) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Supplemental Oil and Gas Information [Abstract]
Balance at beginning of year	$ 9,417	[1]	$ 0	[1]
Reserves acquired in the acquisitions of PXP and MMR	0		14,467	[1]
Sales, net of production expenses	(3,062)		(2,296)	[1]
Net changes in sales and transfer prices, net of production expenses	(2,875)		(459)	[1]
Extensions, discoveries and improved recoveries	194		752	[1]
Changes in estimated future development costs	(498)		(1,190)	[1]
Previously estimated development costs incurred during the year	982		578	[1]
Sales of reserves in-place	(1,323)		(12)	[1]
Other purchases of reserves in-place	487		0	[1]
Revisions of quantity estimates	399		102	[1]
Accretion of discount	1,195		701	[1]
Net change in income taxes	1,505		(3,226)	[1]
Total changes	(2,996)		9,417	[1]
Balance at end of year	$ 6,421		$ 9,417	[1]

[1] Includes the results of FM O&G beginning June 1, 2013.