Hedging - Foreign Currency and Fuel Derivatives Narrative (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Bunker fuel forward contracts
Derivative [Line Items]
Maximum Length of Time Hedged in Price Risk Cash Flow Hedge	3 years
Cost of Sales [Member] \| 30-day euro forward contracts
Derivative [Line Items]
Unrealized gains (losses) on foreign currency derivative instruments not designated as hedges recorded in Net sales		$ (212)
Losses from fluctuations in the value of the net monetary assets exposed to euro exchange rates	$ (10,944)	$ (2,351)

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Amount before tax of foreign currency transaction unrealized gain (loss) recognized in the income statement.

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Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments.

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- Definition

Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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