Risk Management and Trading Activities (Details 5) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Commodity [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	$ 105	$ 225
Derivative contracts not designated as hedging instruments	13,046	11,581
Commodity [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	(299)	(483)
Derivative contracts not designated as hedging instruments	(13,845)	(12,383)
Foreign Exchange [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	8	7
Foreign Exchange [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	(40)	(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	15	10
Derivative contracts not designated as hedging instruments	29	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	(4)	(2)
Derivative contracts not designated as hedging instruments	(32)	(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	120	235
Derivative contracts not designated as hedging instruments	13,083	11,619
Gross fair value of derivative contracts	13,203	11,854
Master netting arrangements	(11,857)	(10,178)
Cash collateral (received) posted	(163)	(213)
Net fair value of derivative contracts	1,183	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	(303)	(485)
Derivative contracts not designated as hedging instruments	(13,917)	(12,434)
Gross fair value of derivative contracts	(14,220)	(12,919)
Master netting arrangements	11,857	10,178
Cash collateral (received) posted	42	34
Net fair value of derivative contracts	$ (2,321)	$ (2,707)