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Effects of Fuel Options Which Were Not Designated as Hedging Instruments (Detail) (Not Designated as Hedging Instrument, Fuel Options, USD $)
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3 Months Ended | 6 Months Ended | 12 Months Ended | |||
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Jun. 30, 2013
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Jun. 30, 2012
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Jun. 30, 2013
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Jun. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Not Designated as Hedging Instrument | Fuel Options
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| Derivative Instruments, Gain (Loss) [Line Items] | ||||||
| Gain recognized in other income (expense) | $ 20,000 | $ 3,218,000 | $ 2,422,000 | |||
| Gain (loss) recognized in other income (expense) | $ (275,000) | $ (366,000) | $ 581,000 | $ 1,715,000 | ||
| X | ||||||||||
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- Definition
Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount of increase in the fair value of derivatives recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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