Fair Value Measurements, Recurring (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Assets:
Investments of certain benefit plans	$ 1,909	$ 1,729
Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	537	1,203
Foreign currency contracts		1
Investments of certain benefit plans	109	98
Total gross fair value, assets	646	1,313
Commodity derivative contracts, net assets	25	14
Net Carrying Value on Balance Sheet, Assets	134	124
Cash Collateral Received Not Offset	0	0
Liabilities:
Commodity derivative contracts	516	1,208
Biofuels blending obligation	11	10
Foreign currency contracts	8	1
Total gross fair value, liabilities	540	1,219
Commodity derivative contracts, net liabilities	5	6
Net Carrying Value on Balance Sheet, Liabilities	29	17
Cash Collateral Paid Not Offset	(76)	(114)
Fair Value, Measurements, Recurring [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts		11
Liabilities:
Physical purchase contracts	5
Fair Value, Inputs, Level 1 [Member]
Assets:
Investments of certain benefit plans	1,136	1,035
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	499	1,143
Foreign currency contracts		1
Investments of certain benefit plans	98	87
Total gross fair value, assets	597	1,231
Liabilities:
Commodity derivative contracts	492	1,138
Biofuels blending obligation	0	0
Foreign currency contracts	8	1
Total gross fair value, liabilities	500	1,139
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts		0
Liabilities:
Physical purchase contracts	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Investments of certain benefit plans	773	694
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	38	60
Foreign currency contracts		0
Investments of certain benefit plans	0	0
Total gross fair value, assets	38	71
Liabilities:
Commodity derivative contracts	24	70
Biofuels blending obligation	11	10
Foreign currency contracts	0	0
Total gross fair value, liabilities	40	80
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts		11
Liabilities:
Physical purchase contracts	5
Fair Value, Inputs, Level 3 [Member]
Assets:
Investments of certain benefit plans	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Commodity derivative contracts	0	0
Foreign currency contracts		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	0
Foreign currency contracts	0	0
Total gross fair value, liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts		0
Liabilities:
Physical purchase contracts	0
Netting [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Effect of Counterparty Netting	(505)	(1,189)
Effect of Cash Collateral Netting	(7)	0
Liabilities:
Effect of Counterparty Netting	(505)	(1,189)
Effect of Cash Collateral Netting	$ (6)	$ (13)