Derivative Instruments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Fuel hedges
Derivative Instruments, Gain (Loss) [Line Items]
Effect on operating income - increase/(decrease)	$ 0.6	[1]	$ 0	[1]	$ 0.6	[1]	$ 0.3	[1]
Effect of mark to market valuation
Derivative Instruments, Gain (Loss) [Line Items]
Effect on operating income - increase/(decrease)	0.6	[1]	(0.2)	[1]	0.6	[1]	0	[1]
Settlements
Derivative Instruments, Gain (Loss) [Line Items]
Effect on operating income - increase/(decrease)	0	[1]	0.2	[1]	0	[1]	0.3	[1]
Foreign exchange hedges
Derivative Instruments, Gain (Loss) [Line Items]
Effect on operating income - increase/(decrease)	$ 0	[2]	$ 0.6	[2]	$ (0.4)	[2]	$ 0	[2]

[1] Included in cost of revenues in the accompanying consolidated statement of operations

[2] Included in other, net in the accompanying consolidated statement of operations