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Assets and Liabilities with Recurring Fair Value Measurements Fair Value Hierarchy (Details) (USD $)
In Millions, unless otherwise specified |
Sep. 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 | $ 1,222 | [1] | $ 1,502 | [1] | ||||||||
| Margin deposits | 302 | [2] | 196 | [2] | ||||||||
| Commodity futures contracts | 505 | 385 | ||||||||||
| Commodity forward contracts | 106 | [3] | 48 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 8 | 4 | ||||||||||
| Total assets | 2,143 | 2,135 | ||||||||||
| Margin deposits held by us posted by our counterparties | 22 | [2],[4] | 11 | [2],[4] | ||||||||
| Commodity futures contracts | 566 | 424 | ||||||||||
| Commodity forward contracts | 95 | [3] | 26 | [3] | ||||||||
| Interest rate swaps | 144 | 200 | ||||||||||
| Liabilities, Fair Value Disclosure | 827 | 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 | 1,222 | [1] | 1,502 | [1] | ||||||||
| Margin deposits | 302 | 196 | ||||||||||
| Commodity futures contracts | 505 | 385 | ||||||||||
| Commodity forward contracts | 0 | [3] | 0 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 0 | 0 | ||||||||||
| Total assets | 2,029 | 2,083 | ||||||||||
| Margin deposits held by us posted by our counterparties | 22 | 11 | ||||||||||
| Commodity futures contracts | 566 | 424 | ||||||||||
| Commodity forward contracts | 0 | [3] | 0 | [3] | ||||||||
| Interest rate swaps | 0 | 0 | ||||||||||
| Liabilities, Fair Value Disclosure | 588 | 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 | 80 | [3] | 24 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 8 | 4 | ||||||||||
| Total assets | 88 | 28 | ||||||||||
| Margin deposits held by us posted by our counterparties | 0 | 0 | ||||||||||
| Commodity futures contracts | 0 | 0 | ||||||||||
| Commodity forward contracts | 85 | [3] | 18 | [3] | ||||||||
| Interest rate swaps | 144 | 200 | ||||||||||
| Liabilities, Fair Value Disclosure | 229 | 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 | 26 | [3] | 24 | [3] | ||||||||
| Interest Rate Swap Assets, Fair Value Disclosure | 0 | 0 | ||||||||||
| Total assets | 26 | 24 | ||||||||||
| Margin deposits held by us posted by our counterparties | 0 | 0 | ||||||||||
| Commodity futures contracts | 0 | 0 | ||||||||||
| Commodity forward contracts | 10 | [3] | 8 | [3] | ||||||||
| Interest rate swaps | 0 | 0 | ||||||||||
| Liabilities, Fair Value Disclosure | $ 10 | $ 8 | ||||||||||
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