Fair Value Measurements and Derivative Instruments (Details 6) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Asset Derivatives
Asset Derivatives	$ 142,358	$ 201,130
Liability Derivatives
Liability Derivatives	164,271	84,344
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	105,533	179,345
Liability Derivatives
Liability Derivatives	112,794	72,357
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	36,825	21,785
Liability Derivatives
Liability Derivatives	51,477	11,987
Interest rate swaps | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	5,978	65,531
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	60,570	11,369
Cross currency swaps | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives		2,914
Foreign currency forward contracts | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	7,112
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	863	1,895
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	7,096
Foreign currency forward contracts | Designated as Hedging Instrument | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	31,728	31,775
Foreign currency forward contracts | Designated as Hedging Instrument | Collars | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	2,678
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	13,251	5,414
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	10,857
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	19,641	11,987
Foreign currency forward contracts | Not Designated as Hedging Instrument | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	19,835
Fuel contracts | Designated as Hedging Instrument | Swaps | Other Assets
Asset Derivatives
Asset Derivatives	18,218	26,258
Fuel contracts | Designated as Hedging Instrument | Swaps | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	73,362	82,747
Fuel contracts | Designated as Hedging Instrument | Swaps | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	9,801	29,213
Fuel contracts | Designated as Hedging Instrument | Swaps | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	921
Fuel contracts | Not Designated as Hedging Instrument | Swaps | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	1,786
Fuel contracts | Not Designated as Hedging Instrument | Swaps | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	1,079
Fuel contracts | Not Designated as Hedging Instrument | Options | Other Assets
Asset Derivatives
Asset Derivatives		16,371
Fuel contracts | Not Designated as Hedging Instrument | Options | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	10,931
Fuel contracts | Not Designated as Hedging Instrument | Options | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	$ 10,922