Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Asset Derivatives
Asset Derivatives		$ 30,883	$ 65,297
Liability Derivatives
Liability Derivatives		385,576	201,812
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	25,705	58,576
Liability Derivatives
Liability Derivatives	[1]	381,738	199,795
Notional Disclosures
Carrying Amount of the Hedged Liabilities		734,811	725,486
Cumulative amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Liabilities		1,097	(24,766)
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		5,178	6,721
Liability Derivatives
Liability Derivatives		3,838	2,017
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	1,415	23,518
Interest rate swaps | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	85,004	40,467
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	13,351	10,844
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	0	4,044
Liability Derivatives
Liability Derivatives	[1]	54,985	39,665
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	144,592	16,854
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		0	1,579
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		3,811	1,751
Liability Derivatives
Liability Derivatives		3,046	808
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives		0	833
Fuel swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	4,241	9,204
Fuel swaps | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	6,698	10,966
Liability Derivatives
Liability Derivatives	[1]	43,160	37,627
Fuel swaps | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	53,997	65,182
Fuel swaps | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		243	587
Fuel swaps | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		1,124	2,804
Liability Derivatives
Liability Derivatives		370	376
Fuel swaps | Not Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives		$ 422	$ 0

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