Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
Asset Derivatives
Asset Derivatives		$ 39,045	$ 39,994
Liability Derivatives
Liability Derivatives		404,284	257,728
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	38,874	34,990
Liability Derivatives
Liability Derivatives	[1]	367,355	255,005
Notional Disclosures
Carrying Amount of the Hedged Liabilities		721,611	715,234
Cumulative amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Liabilities		21,934	(1,301)
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		171	5,004
Liability Derivatives
Liability Derivatives		36,929	2,723
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	21,695	11
Interest rate swaps | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	102,687	64,168
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	16,482	9,380
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	697	0
Liability Derivatives
Liability Derivatives	[1]	83,034	75,260
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	60,887	64,711
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		0	0
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		171	3,186
Liability Derivatives
Liability Derivatives		165	2,419
Foreign currency forward contracts | Not Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives		0	0
Fuel swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	0	8,677
Fuel swaps | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	0	16,922
Liability Derivatives
Liability Derivatives	[1]	40,285	16,901
Fuel swaps | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	80,462	33,965
Fuel swaps | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		0	175
Fuel swaps | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		0	1,643
Liability Derivatives
Liability Derivatives		35,334	295
Fuel swaps | Not Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives		$ 1,430	$ 9

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