Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Asset Derivatives
Asset Derivatives		$ 16,297	$ 19,397
Liability Derivatives
Liability Derivatives		357,973	373,497
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	15,982	18,854
Liability Derivatives
Liability Derivatives	[1]	343,123	356,029
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		315	543
Liability Derivatives
Liability Derivatives		14,850	17,468
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	5,935	5,246
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	53,274	57,679
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	605	0
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	614	0
Liability Derivatives
Liability Derivatives	[1]	12,896	5,574
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	54,073	68,165
Fuel swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	8,345	13,608
Fuel swaps | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	483	0
Liability Derivatives
Liability Derivatives	[1]	130,815	129,486
Fuel swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	92,065	95,125
Fuel swaps | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		315	543
Fuel swaps | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		0	0
Liability Derivatives
Liability Derivatives		10,110	11,532
Fuel swaps | Not Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives		$ 4,740	$ 5,936

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