Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Asset Derivatives
Asset Derivatives		$ 41,633	$ 134,574
Liability Derivatives
Liability Derivatives		614,150	1,044,292
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	38,041	93,996
Liability Derivatives
Liability Derivatives	[1]	597,928	1,020,774
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		3,592	40,578
Liability Derivatives
Liability Derivatives		16,222	23,518
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	23,032	0
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	164,060	67,371
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	0	0
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	0	93,996
Liability Derivatives
Liability Derivatives	[1]	9,548	320,873
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	17,488	0
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		0	32,339
Liability Derivatives
Liability Derivatives		0	0
Fuel swaps | Designated as Hedging Instrument | Swaps | Other assets
Asset Derivatives
Asset Derivatives	[1]	15,009	0
Fuel swaps | Designated as Hedging Instrument | Swaps | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	0	0
Liability Derivatives
Liability Derivatives	[1]	211,973	307,475
Fuel swaps | Designated as Hedging Instrument | Swaps | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	194,859	325,055
Fuel swaps | Not Designated as Hedging Instrument | Swaps | Derivative financial instruments
Asset Derivatives
Asset Derivatives		3,592	8,239
Liability Derivatives
Liability Derivatives		$ 16,222	$ 23,518

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