Fair Value Measurements and Derivative Instruments (Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Asset Derivatives
Asset Derivatives	$ 108,539	$ 39,994
Liability Derivatives
Liability Derivatives	259,705	257,728
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	107,705	34,990
Liability Derivatives
Liability Derivatives	240,573	255,005
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	834	5,004
Liability Derivatives
Liability Derivatives	19,132	2,723
Interest rate swaps | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	17,271	11
Interest rate swaps | Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	261	0
Liability Derivatives
Liability Derivatives	0	0
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	144,653	64,168
Foreign currency forward contracts | Designated as Hedging Instrument | Other Assets
Asset Derivatives
Asset Derivatives	20,836	9,380
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	63,894	0
Liability Derivatives
Liability Derivatives	13,294	75,260
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	7,306	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	0	3,186
Liability Derivatives
Liability Derivatives	160	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	350	8,677
Fuel swaps | Designated as Hedging Instrument | Derivative Financial Instruments
Asset Derivatives
Asset Derivatives	5,093	16,922
Liability Derivatives
Liability Derivatives	25,203	16,901
Fuel swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	50,117	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	834	1,643
Liability Derivatives
Liability Derivatives	18,028	295
Fuel swaps | Not Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	$ 944	$ 9