Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Derivatives - Effects of Fuel Options Which Were Not Designated as Hedging Instruments (Detail)

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Fair Value Measurements and Derivatives - Effects of Fuel Options Which Were Not Designated as Hedging Instruments (Detail) (Not Designated as Hedging Instrument, Fuel Options, USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Not Designated as Hedging Instrument | Fuel Options
        
Derivative Instruments, Gain (Loss) [Line Items]        
Gain recognized in other income $ 101 $ (275) $ 186 $ 581