Derivatives and Hedging Activities Derivative Instruments in Balance Sheet Table (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Liability Derivatives:
Total derivative instruments	$ (979)	$ (1,719)
Designated as Hedging Instrument
Liability Derivatives:
Liability commodity contracts	(20)	(38)
Designated as Hedging Instrument | Foreign currency contracts | Long-term derivative instruments
Liability Derivatives:
Liability commodity contracts	(20)	(38)
Not designated as hedging instruments
Asset Derivatives:
Asset commodity contracts	115	55
Liability Derivatives:
Liability commodity contracts	(1,074)	(1,736)
Not designated as hedging instruments | Commodity contracts | Short-term derivative instruments
Asset Derivatives:
Asset commodity contracts	110	54
Liability Derivatives:
Liability commodity contracts	(157)	(232)
Not designated as hedging instruments | Commodity contracts | Long-term derivative instruments
Asset Derivatives:
Asset commodity contracts	5	1
Liability Derivatives:
Liability commodity contracts	(882)	(1,462)
Not designated as hedging instruments | Interest rate contracts | Long-term derivative instruments
Liability Derivatives:
Liability commodity contracts	$ (35)	$ (42)