Fair Value Measurements, Recurring (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	$ 170	$ 176
Physical purchase contracts	(36)	(2)
Investments of certain benefit plans	100	95
Foreign currency contracts	1
Other investments	0	0
Liabilities:
Commodity derivative contracts	8	25
Biofuels blending obligation	3
Obligations of certain benefit plans	36	34
Foreign currency contracts	3	3
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	2,310	2,038
Physical purchase contracts	0	0
Investments of certain benefit plans	89	84
Foreign currency contracts	1
Other investments	0	0
Liabilities:
Commodity derivative contracts	2,145	1,864
Biofuels blending obligation	3
Obligations of certain benefit plans	36	34
Foreign currency contracts	3	3
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	162	78
Physical purchase contracts	(36)	(2)
Investments of certain benefit plans	0	0
Foreign currency contracts	0
Other investments	0	0
Liabilities:
Commodity derivative contracts	165	101
Biofuels blending obligation	0
Obligations of certain benefit plans	0	0
Foreign currency contracts	0	0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	0	0
Physical purchase contracts	0	0
Investments of certain benefit plans	11	11
Foreign currency contracts	0
Other investments	0	0
Liabilities:
Commodity derivative contracts	0	0
Biofuels blending obligation	0
Obligations of certain benefit plans	0	0
Foreign currency contracts	0	0
Netting and Collateral [Member]
Fair Value Measurements (Textual)
Cash collateral received from (payable to) brokers	199	136
Netting and Collateral [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	(2,302)	(1,940)
Physical purchase contracts	0	0
Investments of certain benefit plans	0	0
Foreign currency contracts	0
Other investments	0	0
Liabilities:
Commodity derivative contracts	(2,302)	(1,940)
Biofuels blending obligation	0
Obligations of certain benefit plans	0	0
Foreign currency contracts	$ 0	$ 0

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Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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Cash Collateral Received From (Payable To) Brokers.

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Credit adjustments made in the current period to the value and amount of inventory reported related to firm commitments to purchases inventory.

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