CAPITALIZED EXPLORATORY WELL COSTS - Capitalized Exploratory Well Costs Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized exploratory well costs, Beginning Balance	$ 264	$ 245	$ 849
Additions pending determination of proved reserves	477	249	382
Divestitures and other	(3)	0	(557)
Reclassifications to proved properties	(373)	(211)	(369)
Charged to exploration expense	(15)	(19)	(60)
Capitalized exploratory well costs, Ending Balance	$ 350	264	245
Canada
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized exploratory well costs, Beginning Balance		$ 2
Capitalized exploratory well costs, Ending Balance			$ 2