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Assets and Liabilities with Recurring Fair Value Measurements Fair Value Hierarchy (Details) (USD $)
In Millions, unless otherwise specified |
Jun. 30, 2013
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Dec. 31, 2012
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|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||||||
| Cash equivalents | $ 871 | [1] | $ 1,502 | [1] | ||||||||
| Margin deposits | 276 | [2] | 196 | [2] | ||||||||
| Commodity futures contracts | 595 | 385 | ||||||||||
| Commodity forward contracts | 134 | [3] | 48 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 8 | 4 | ||||||||||
| Total assets | 1,884 | 2,135 | ||||||||||
| Margin deposits held by us posted by our counterparties | 3 | [2],[4] | 11 | [2],[4] | ||||||||
| Commodity futures contracts | 646 | 424 | ||||||||||
| Commodity forward contracts | 130 | [3] | 26 | [3] | ||||||||
| Interest rate swaps | 145 | 200 | ||||||||||
| Liabilities, Fair Value Disclosure | 924 | 661 | ||||||||||
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Fair Value, Inputs, Level 1 [Member]
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||||||
| Cash equivalents | 871 | [1] | 1,502 | [1] | ||||||||
| Margin deposits | 276 | 196 | ||||||||||
| Commodity futures contracts | 595 | 385 | ||||||||||
| Commodity forward contracts | 0 | [3] | 0 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 0 | 0 | ||||||||||
| Total assets | 1,742 | 2,083 | ||||||||||
| Margin deposits held by us posted by our counterparties | 3 | 11 | ||||||||||
| Commodity futures contracts | 646 | 424 | ||||||||||
| Commodity forward contracts | 0 | [3] | 0 | [3] | ||||||||
| Interest rate swaps | 0 | 0 | ||||||||||
| Liabilities, Fair Value Disclosure | 649 | 435 | ||||||||||
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Fair Value, Inputs, Level 2 [Member]
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||||||
| Cash equivalents | 0 | [1] | 0 | [1] | ||||||||
| Margin deposits | 0 | 0 | ||||||||||
| Commodity futures contracts | 0 | 0 | ||||||||||
| Commodity forward contracts | 112 | [3] | 24 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 8 | 4 | ||||||||||
| Total assets | 120 | 28 | ||||||||||
| Margin deposits held by us posted by our counterparties | 0 | 0 | ||||||||||
| Commodity futures contracts | 0 | 0 | ||||||||||
| Commodity forward contracts | 121 | [3] | 18 | [3] | ||||||||
| Interest rate swaps | 145 | 200 | ||||||||||
| Liabilities, Fair Value Disclosure | 266 | 218 | ||||||||||
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Fair Value, Inputs, Level 3 [Member]
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||||||
| Cash equivalents | 0 | [1] | 0 | [1] | ||||||||
| Margin deposits | 0 | 0 | ||||||||||
| Commodity futures contracts | 0 | 0 | ||||||||||
| Commodity forward contracts | 22 | [3] | 24 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 0 | 0 | ||||||||||
| Total assets | 22 | 24 | ||||||||||
| Margin deposits held by us posted by our counterparties | 0 | 0 | ||||||||||
| Commodity futures contracts | 0 | 0 | ||||||||||
| Commodity forward contracts | 9 | [3] | 8 | [3] | ||||||||
| Interest rate swaps | 0 | 0 | ||||||||||
| Liabilities, Fair Value Disclosure | $ 9 | $ 8 | ||||||||||
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