Risk Management and Trading Activities (Details 5) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Commodity Contracts [Member] | Accounts Receivable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts designated as hedging instruments	$ 97	$ 225
Derivative contracts not designated as hedging instruments	12,040	11,581
Commodity Contracts [Member] | Accounts Payable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts designated as hedging instruments	(281)	(483)
Derivative contracts not designated as hedging instruments	(12,657)	(12,383)
Foreign Exchange Contracts [Member] | Accounts Receivable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts not designated as hedging instruments	6	7
Foreign Exchange Contracts [Member] | Accounts Payable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts not designated as hedging instruments	(41)	(19)
Other [Member] | Accounts Receivable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts designated as hedging instruments	56	10
Derivative contracts not designated as hedging instruments	60	31
Other [Member] | Accounts Payable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts designated as hedging instruments	(3)	(2)
Derivative contracts not designated as hedging instruments	(107)	(32)
Accounts Receivable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts designated as hedging instruments	153	235
Derivative contracts not designated as hedging instruments	12,106	11,619
Gross fair value of derivative contracts	12,259	11,854
Master netting arrangements	(10,897)	(10,178)
Cash collateral (received) posted	(133)	(213)
Net fair value of derivative contracts	1,229	1,463
Accounts Payable [Member]
Gross and net fair values of the Corporation's risk management and trading derivative instruments
Derivative contracts designated as hedging instruments	(284)	(485)
Derivative contracts not designated as hedging instruments	(12,805)	(12,434)
Gross fair value of derivative contracts	(13,089)	(12,919)
Master netting arrangements	10,897	10,178
Cash collateral (received) posted	85	34
Net fair value of derivative contracts	$ (2,107)	$ (2,707)