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Effects of Derivatives Designated as Cash Flow Hedges (Detail)

v2.4.0.8
Effects of Derivatives Designated as Cash Flow Hedges (Detail) (Cash Flow Hedge, Fuel Swaps, USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Cash Flow Hedge | Fuel Swaps
              
Fair Value, Option, Quantitative Disclosures [Line Items]              
Gain recognized in other comprehensive income (loss)-effective portion         $ 18,906 $ 29,928 $ 5,851
Loss recognized in other comprehensive (loss) - effective portion (18,074) (34,283) (13,368) (7,819)      
Gain (loss) recognized in other income (expense)-ineffective portion         (509) 457 140
Loss recognized in other income (expense)- ineffective portion (320) (1,843) (99) (599)      
Amount reclassified from accumulated other comprehensive income (loss) into fuel expense (736) (3,093) (2,999) (12,332) (14,448) (36,686) (3,065)
Effect of derivative on consolidated financial statements         $ 3,949 $ (6,301) $ 2,926