| Fair Value Measurements and Derivatives - Effects of fuel swaps dedesignated and recognized into earnings (Details 3) - Fuel Swaps - Dedesignated As Hedging Instrument - USD ($) $ in Thousands | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | |
| Derivatives Fair Value [Line Items] | |||
| Amount reclassified from accumulated other comprehensive income (loss) into other income (expense) | $ 10,000 | ||
| Loss recognized in other income (expense) | $ (4,727) | ||
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- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of 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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- 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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