Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Asset Derivatives
Asset Derivatives	$ 131,128		$ 63,981
Liability Derivatives
Liability Derivatives	968,464		767,635
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	131,128	[1]	63,981	[1]
Liability Derivatives
Liability Derivatives	933,584	[1]	767,635	[1]
Designated as Hedging Instrument | Foreign currency collar options | Other assets
Asset Derivatives
Asset Derivatives	0	[1]	0	[1]
Designated as Hedging Instrument | Foreign currency collar options | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	69,857	[1]	21,855	[1]
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	0		0
Liability Derivatives
Liability Derivatives	34,880		0
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	821	[1]	0	[1]
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	80,429	[1]	65,768	[1]
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	130,292	[1]	63,981	[1]
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	0	[1]	0	[1]
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	318,789	[1]	164,627	[1]
Foreign currency forward contracts | Designated as Hedging Instrument | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	28,368	[1]	17,619	[1]
Fuel swaps | Designated as Hedging Instrument | Swaps | Other assets
Asset Derivatives
Asset Derivatives	15	[1]	0	[1]
Fuel swaps | Designated as Hedging Instrument | Swaps | Derivative financial instruments
Asset Derivatives
Asset Derivatives	0	[1]	0	[1]
Fuel swaps | Designated as Hedging Instrument | Swaps | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	235,739	[1]	270,254	[1]
Fuel swaps | Designated as Hedging Instrument | Swaps | Accrued expenses and other liabilities
Liability Derivatives
Liability Derivatives	200,402	[1]	227,512	[1]
Fuel swaps | Not Designated as Hedging Instrument | Swaps | Other assets
Asset Derivatives
Asset Derivatives	0		0
Fuel swaps | Not Designated as Hedging Instrument | Swaps | Derivative financial instruments
Asset Derivatives
Asset Derivatives	0		0
Liability Derivatives
Liability Derivatives	19,624		0
Fuel swaps | Not Designated as Hedging Instrument | Swaps | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	$ 15,256		$ 0

[1] Accounting Standard Codification 815-20 “Derivatives and Hedging.”