| Fair Value Measurements and Derivatives (Detail Textuals) In Millions, unless otherwise specified | 9 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|
| Sep. 30, 2014
 USD ($) | Dec. 31, 2013
 USD ($) | Sep. 30, 2014
 Fuel Swaps
 Metric_Ton | Sep. 30, 2014
 Fuel Swaps
 Maximum | Sep. 30, 2014
 Fuel Collars and Fuel Options
 Maximum
 Metric_Ton | Sep. 30, 2014
 Interest Rate Swap
 USD ($) | Sep. 30, 2014
 Foreign Exchange Forward
 USD ($) | Sep. 30, 2014
 Foreign Exchange Forward
 EUR (€) | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||||||||
| Derivative maturing date | Dec. 31, 2017 | Dec. 31, 2014 | ||||||
| Projected fuel purchases | 717,000 | 9,000 | ||||||
| Notional amount of derivatives | $ 627.5 | $ 365.0 | € 289.0 | |||||
| Fair value of long-term debt | 3,571.3 | 3,146.4 | ||||||
| Fair value of long-term debt in excess of carrying value | $ 107.4 | $ 18.6 | ||||||
| X | ||||||||||
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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Date the derivative contract matures, in CCYY-MM-DD format. No definition available. 
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- Details 
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| X | ||||||||||
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- Definition This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of long-term debt instruments that have contractual principal amounts and for which the fair value option has been elected. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. No definition available. 
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