Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
Asset Derivatives
Asset Derivatives		$ 36,697	$ 134,574
Liability Derivatives
Liability Derivatives		507,202	1,044,292
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	35,335	93,996
Liability Derivatives
Liability Derivatives	[1]	479,430	1,020,774
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		1,362	40,578
Liability Derivatives
Liability Derivatives		27,772	23,518
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	15,371	0
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	139,322	67,371
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	6,926	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]	136	320,873
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	7,392	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 | Other assets
Asset Derivatives
Asset Derivatives	[1]	13,038	0
Fuel swaps | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	0	0
Liability Derivatives
Liability Derivatives	[1]	183,470	307,475
Fuel swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	149,110	325,055
Fuel swaps | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		434	0
Fuel swaps | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		928	8,239
Liability Derivatives
Liability Derivatives		18,271	23,518
Fuel swaps | Not Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives		$ 9,501	$ 0

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