Fair Value Measurements, Recurring (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets:
Commodity derivative contracts	$ 1,043	$ 1,203
Foreign currency contracts	10	1
Investments of certain benefit plans	103	98
Total gross fair value, assets	1,161	1,313
Commodity derivative contracts, net assets	43	14
Net Carrying Value on Balance Sheet, Assets	161	124
Cash Collateral Received Not Offset	0	0
Liabilities:
Commodity derivative contracts	1,025	1,208
Biofuels blending obligation		10
Foreign currency contracts		1
Total gross fair value, liabilities	1,058	1,219
Commodity derivative contracts, net liabilities	5	6
Net Carrying Value on Balance Sheet, Liabilities	38	17
Cash Collateral Paid Not Offset	(109)	(114)
Fair Value Measurements (Textual)
Fair value asset transfers from Level 1 to Level 2	0	0
Fair value asset transfers from Level 2 to Level 1	0	0
Fair value liability transfers from level 1 to level 2	0	0
Fair value liability transfers from level 2 to level 1	0	0
Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	5	11
Liabilities:
Physical purchase and fixed-price contracts	11
RINs Fixed-Price Contracts [Member]
Liabilities:
Physical purchase and fixed-price contracts	22
Fair Value, Inputs, Level 1 [Member]
Assets:
Commodity derivative contracts	1,015	1,143
Foreign currency contracts	10	1
Investments of certain benefit plans	92	87
Total gross fair value, assets	1,117	1,231
Liabilities:
Commodity derivative contracts	997	1,138
Biofuels blending obligation		0
Foreign currency contracts		1
Total gross fair value, liabilities	997	1,139
Fair Value, Inputs, Level 1 [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	0	0
Liabilities:
Physical purchase and fixed-price contracts	0
Fair Value, Inputs, Level 1 [Member] | RINs Fixed-Price Contracts [Member]
Liabilities:
Physical purchase and fixed-price contracts	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Commodity derivative contracts	28	60
Foreign currency contracts	0	0
Investments of certain benefit plans	0	0
Total gross fair value, assets	33	71
Liabilities:
Commodity derivative contracts	28	70
Biofuels blending obligation		10
Foreign currency contracts		0
Total gross fair value, liabilities	61	80
Fair Value, Inputs, Level 2 [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	5	11
Liabilities:
Physical purchase and fixed-price contracts	11
Fair Value, Inputs, Level 2 [Member] | RINs Fixed-Price Contracts [Member]
Liabilities:
Physical purchase and fixed-price contracts	22
Fair Value, Inputs, Level 3 [Member]
Assets:
Commodity derivative contracts	0	0
Foreign currency contracts	0	0
Investments of certain benefit plans	11	11
Total gross fair value, assets	11	11
Liabilities:
Commodity derivative contracts	0	0
Biofuels blending obligation		0
Foreign currency contracts		0
Total gross fair value, liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	0	0
Liabilities:
Physical purchase and fixed-price contracts	0
Fair Value, Inputs, Level 3 [Member] | RINs Fixed-Price Contracts [Member]
Liabilities:
Physical purchase and fixed-price contracts	0
Netting [Member]
Assets:
Effect of Counterparty Netting	(997)	(1,189)
Effect of Cash Collateral Netting	(3)	0
Liabilities:
Effect of Counterparty Netting	(997)	(1,189)
Effect of Cash Collateral Netting	$ (23)	$ (13)