Fair Value Measurements and Derivatives - Consolidated financial statements of fuel swaps dedesignated and immediately recognized into earnings (Details 3) - USD ($) $ in Thousands  | 
3 Months Ended | |
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Mar. 31, 2017  | 
Mar. 31, 2016  | 
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| Reclassification out of Accumulated Other Comprehensive Income | Fuel Swaps | ||
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] | ||
| Amount reclassified from accumulated other comprehensive income (loss) into other income (expense), net | $ 1,529 | |
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- Definition Amount of revenue and income classified as other. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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