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Derivative Instruments and Hedges - Schedule of Information About Effect of Derivative Instruments on Accumulated Other Comprehensive Income and Consolidated Statements of Operations (Detail) (Commodity swaps, USD $)
In Thousands, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Designated as Hedging Instrument | |||
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Loss Recognized in Accumulated OCI | $ 0 | $ 0 | $ (1,365) |
| Loss Reclassified from Accumulated OCI | 0 | 0 | (283) |
| Gain (Loss) Recognized on Derivatives | 0 | 0 | (50) |
| Not Designated as Hedging Instrument | |||
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Loss Reclassified from Accumulated OCI | 0 | (335) | (5,573) |
| Gain (Loss) Recognized on Derivatives | $ 4,290 | $ 16,117 | $ (2,973) |