Fair Value Measurements and Derivative Instruments (Income Statement) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fuel Expense	$ 371,015	$ 697,962	$ 710,617
Depreciation and amortization expenses	1,279,254	1,245,942	1,033,697
Interest Income (Expense)	(823,202)	(381,568)	(300,872)
Other Income (Expense)	(137,085)	(24,513)	11,107
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(79,119)	5,205
Interest contracts | Interest Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(25,267)	(4,289)
Fuel swaps | Other Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	3,549	(1,292)
Fuel swaps | Fuel Expense
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(35,407)	29,929
Foreign exchange contracts | Other Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(7,315)	(5,080)
Foreign exchange contracts | Depreciation and Amortization Expenses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(14,679)	(14,063)
Fair value hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value hedge	(18,813)	(23,464)	4,673
Change in unrealized gain (loss) on fair value hedging instruments	23,819	16,607	(8,854)
Fair value hedging | Interest contracts | Interest Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value hedge	(18,813)	(23,464)	4,673
Change in unrealized gain (loss) on fair value hedging instruments	23,819	16,607	(8,854)
Fair value hedging | Interest contracts | Other Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value hedge	0	0	0
Change in unrealized gain (loss) on fair value hedging instruments	$ 0	$ 0	0
Cash flow hedge | Interest contracts | Interest Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income			(10,931)
Cash flow hedge | Fuel swaps | Other Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income			(1,580)
Cash flow hedge | Fuel swaps | Fuel Expense
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income			1,366
Cash flow hedge | Foreign exchange contracts | Other Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income			12,855
Cash flow hedge | Foreign exchange contracts | Depreciation and Amortization Expenses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income			$ (12,843)