General Information (Unaudited) (Details) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Oct. 31, 2015	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2015 $ / bbl	Sep. 30, 2015 USD ($) $ / bbl	Sep. 30, 2014 USD ($)
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Fair Value Inputs, Discount Rate					10.00%
Impairment of oil and gas properties		$ (3,652)	$ (308)		$ (9,442)	$ (308)
Accumulated Costs Related to Unproved Properties Transferred to Full Cost Pool		837
Restructuring Costs and Asset Impairment Charges		$ 36
Crude Oil [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Average Sales Prices | $ / bbl				71.68	59.21
Tyrone [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Reduction in Operating Rates, Percent		50.00%
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		$ 59
El Abra [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Reduction in Operating Rates, Percent		50.00%
Henderson [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Reduction in Operating Rates, Percent		35.00%
Subsequent Event [Member] | Sierrita [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Reduction in Operating Rates, Percent	50.00%