Derivative and Hedging Activities - Derivative Instruments in Balance Sheet Table (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	$ (249)	$ (649)
Derivative, Gain (Loss) on Derivative, Net	0	0
Short-term derivative assets	100	0
Long-term derivative assets	14	4
Derivative Liability, Current	(71)	(208)
Long-term derivative liabilities	(294)	(445)
Derivative Assets (Liabilities), at Fair Value, Net	(249)	(649)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	(167)	(553)
Derivative, Gain (Loss) on Derivative, Net	0	0
Derivative Assets (Liabilities), at Fair Value, Net	(167)	(553)
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	(52)	(98)
Derivative, Gain (Loss) on Derivative, Net	0	0
Derivative Assets (Liabilities), at Fair Value, Net	(52)	(98)
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	(30)	2
Derivative, Gain (Loss) on Derivative, Net	0	0
Derivative Assets (Liabilities), at Fair Value, Net	(30)	2
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	193	29
Derivative, Gain (Loss) on Derivative, Net	(93)	(29)
Short-term derivative assets	100	0
Other Noncurrent Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	26	11
Derivative, Gain (Loss) on Derivative, Net	(12)	(9)
Long-term derivative assets	14	2
Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(155)	(231)
Derivative, Gain (Loss) on Derivative, Net	93	29
Derivative Liability, Current	(62)	(202)
Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(7)	(6)
Derivative, Gain (Loss) on Derivative, Net	0	0
Derivative Liability, Current	(7)	(6)
Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(231)	(362)
Derivative, Gain (Loss) on Derivative, Net	12	9
Long-term derivative liabilities	(219)	(353)
Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(45)	(92)
Derivative, Gain (Loss) on Derivative, Net	0	0
Long-term derivative liabilities	(45)	(92)
Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		2
Derivative liability, gross liability	(30)
Derivative, Gain (Loss) on Derivative, Net	0	0
Long-term derivative assets		2
Long-term derivative liabilities	$ (30)