Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Asset Derivatives
Asset Derivatives		$ 137,463	$ 134,574
Liability Derivatives
Liability Derivatives		1,017,967	1,044,292
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	95,118	93,996
Liability Derivatives
Liability Derivatives	[1]	864,266	1,020,774
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		42,345	40,578
Liability Derivatives
Liability Derivatives		153,701	23,518
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	13,046	0
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	139,805	67,371
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	78,179	93,996
Liability Derivatives
Liability Derivatives	[1]	139,456	320,873
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		33,779	32,339
Liability Derivatives
Liability Derivatives		129,817	0
Fuel swaps | Designated as Hedging Instrument | Swaps | Other assets
Asset Derivatives
Asset Derivatives	[1]	3,893	0
Fuel swaps | Designated as Hedging Instrument | Swaps | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	0	0
Liability Derivatives
Liability Derivatives	[1]	284,336	307,475
Fuel swaps | Designated as Hedging Instrument | Swaps | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	300,669	325,055
Fuel swaps | Not Designated as Hedging Instrument | Swaps | Derivative financial instruments
Asset Derivatives
Asset Derivatives		8,566	8,239
Liability Derivatives
Liability Derivatives		$ 23,884	$ 23,518

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