Annual report pursuant to Section 13 and 15(d)

Effects of Fuel Options Which Were Not Designated as Hedging Instruments (Detail)

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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
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Not Designated as Hedging Instrument | Fuel Options
      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain recognized in other income (expense) $ 1,340 $ 3,218 $ 2,422