Leases and Prepaid Maintenance Deposits - Fixed Maintenance Reserve Payments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Leases And Prepaid Maintenance Deposits [Abstract]
Estimated fixed maintenance reserve payments, 2013	$ 10.3
Estimated fixed maintenance reserve payments, 2014	10.6
Estimated fixed maintenance reserve payments, 2015	11.0
Estimated fixed maintenance reserve payments, 2016	11.4
Estimated fixed maintenance reserve payments, 2017	11.1
Estimated fixed maintenance reserve payments, 2018 and beyond	$ 40.4

Fixed Maintenance Reserve Payments, Future Estimated Payments Due, Due in Five Years

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Fixed Maintenance Reserve Payments, Future Estimated Payments Due, Due in Four Years

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Fixed Maintenance Reserve Payments, Future Estimated Payments Due, Due in Three Years

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Fixed Maintenance Reserve Payments, Future Estimated Payments Due, Due in Two Years

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Fixed Maintenance Reserve Payments, Future Estimated Payments Due, Due Thereafter

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Fixed Maintenance Reserve Payments, Future Estimated Payments Due, Next Twelve Months

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