Derivative and Hedging Activities - Derivative Instruments in Balance Sheet Table (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 515	$ 512
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Fair Value, Net	515	512	$ 512
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	241	267
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	241	267
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Fair Value, Net	241	267
Not Designated as Hedging Instrument [Member] \| Supply Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	317	297
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Fair Value, Net	317	297
Not Designated as Hedging Instrument [Member] \| Other Current Assets [Member] \| Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	345	381
Derivative Asset, Fair Value, Gross Liability	(49)	(66)
Derivative, Fair Value, Net	296	315
Not Designated as Hedging Instrument [Member] \| Other Current Assets [Member] \| Supply Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	54	51
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative, Fair Value, Net	54	51
Not Designated as Hedging Instrument [Member] \| Other Noncurrent Assets [Member] \| Supply Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	263	246
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative, Fair Value, Net	263	246
Not Designated as Hedging Instrument [Member] \| Other Current Liabilities [Member] \| Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(92)	(106)
Derivative Liability, Fair Value, Gross Asset	49	66
Derivative, Fair Value, Net	(43)	(40)
Not Designated as Hedging Instrument [Member] \| Other Noncurrent Liabilities [Member] \| Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(12)	(8)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Fair Value, Net	(12)	(8)
Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(43)	(52)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Fair Value, Net	(43)	(52)
Designated as Hedging Instrument [Member] \| Other Current Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(43)
Derivative Liability, Fair Value, Gross Asset	0
Derivative, Fair Value, Net	$ (43)
Designated as Hedging Instrument [Member] \| Other Noncurrent Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability		(52)
Derivative Liability, Fair Value, Gross Asset		0
Derivative, Fair Value, Net		$ (52)

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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