Derivatives (Open Commodity Derivative Contracts) (Detail)
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6 Months Ended | |||||
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Jun. 30, 2012
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Crude Oil Exchange-Traded [Member]
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Derivative [Line Items] | ||||||
Percentage of derivative contracts expiring in the period | 99.10% | |||||
Derivative contract expiration date | Sep. 30, 2012 | |||||
Refined Products Exchange-Traded [Member]
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Derivative [Line Items] | ||||||
Percentage of derivative contracts expiring in the period | 100.00% | |||||
Derivative contract expiration date | Sep. 30, 2012 | |||||
Long [Member] | Crude Oil Exchange-Traded [Member]
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Derivative [Line Items] | ||||||
Notional Contracts (in thousands of Total Barrels) | 14,023 | [1] | ||||
Long [Member] | Refined Products Exchange-Traded [Member]
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Derivative [Line Items] | ||||||
Notional Contracts (in thousands of Total Barrels) | 3,124 | [2] | ||||
Short [Member] | Crude Oil Exchange-Traded [Member]
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Derivative [Line Items] | ||||||
Notional Contracts (in thousands of Total Barrels) | (26,774) | [1] | ||||
Short [Member] | Refined Products Exchange-Traded [Member]
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Derivative [Line Items] | ||||||
Notional Contracts (in thousands of Total Barrels) | (7,062) | [2] | ||||
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