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Derivative Instruments - Put and Call Option Contracts (Phantom) (Details)
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12 Months Ended | |
|---|---|---|
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Dec. 31, 2014
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Dec. 31, 2013
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| Minimum | Unleaded Fuel | ||
| Derivative [Line Items] | ||
| Option contracts settlement date | 2015-01 | 2014-01 |
| Minimum | Diesel | ||
| Derivative [Line Items] | ||
| Option contracts settlement date | 2015-01 | 2014-01 |
| Maximum | Unleaded Fuel | ||
| Derivative [Line Items] | ||
| Option contracts settlement date | 2016-03 | 2015-06 |
| Maximum | Diesel | ||
| Derivative [Line Items] | ||
| Option contracts settlement date | 2016-03 | 2015-06 |