Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Asset Derivatives
Asset Derivatives		$ 97,519	$ 108,539
Liability Derivatives
Liability Derivatives		173,193	259,705
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	88,548	107,705
Liability Derivatives
Liability Derivatives	[1]	173,193	240,573
Notional Disclosures
Carrying Amount of the Hedged Liabilities		659,209	700,331
Cumulative amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Liabilities		10,413	17,512
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		8,971	834
Liability Derivatives
Liability Derivatives		0	19,132
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	10,407	17,271
Interest rate swaps | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	16	261
Liability Derivatives
Liability Derivatives	[1]	0	0
Interest rate swaps | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	88,891	144,653
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	0	20,836
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	19,143	63,894
Liability Derivatives
Liability Derivatives	[1]	79,305	13,294
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	4,997	7,306
Foreign currency forward contracts | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		0	0
Liability Derivatives
Liability Derivatives		0	160
Fuel swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	16,080	350
Fuel swaps | Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives	[1]	42,902	5,093
Liability Derivatives
Liability Derivatives	[1]	0	25,203
Fuel swaps | Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives	[1]	0	50,117
Fuel swaps | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		625	0
Fuel swaps | Not Designated as Hedging Instrument | Derivative financial instruments
Asset Derivatives
Asset Derivatives		8,346	834
Liability Derivatives
Liability Derivatives		0	18,028
Fuel swaps | Not Designated as Hedging Instrument | Other long-term liabilities
Liability Derivatives
Liability Derivatives		$ 0	$ 944

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