Fair Value Measurements and Derivative Instruments (Details 6) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Asset Derivatives
Asset Derivatives	$ 156,105	$ 201,130
Liability Derivatives
Liability Derivatives	195,593	84,344
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	114,356	179,345
Liability Derivatives
Liability Derivatives	147,277	72,357
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	41,749	21,785
Liability Derivatives
Liability Derivatives	48,316	11,987
Interest rate swaps | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	65,729	65,531
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	41,147	11,369
Cross currency swaps | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives		2,914
Cross currency swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	2,140
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	211	1,895
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	11,035
Foreign currency forward contracts | Designated as Hedging Instrument | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	39,895	31,775
Foreign currency forward contracts | Designated as Hedging Instrument | Collars | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	6,906
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	18,912	5,414
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	13,931
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	25,459	11,987
Foreign currency forward contracts | Not Designated as Hedging Instrument | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	22,857
Fuel contracts | Designated as Hedging Instrument | Swaps | Other Assets
Asset Derivatives
Asset Derivatives	11,003	26,258
Fuel contracts | Designated as Hedging Instrument | Swaps | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	37,413	82,747
Fuel contracts | Designated as Hedging Instrument | Swaps | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	40,160	29,213
Fuel contracts | Designated as Hedging Instrument | Swaps | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	5,994
Fuel contracts | Not Designated as Hedging Instrument | Options | Other Assets
Asset Derivatives
Asset Derivatives	5,165	16,371
Fuel contracts | Not Designated as Hedging Instrument | Options | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	$ 3,741