Changes in Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	$ 102,038	$ 86,510	$ 313,757	$ 236,252
Depreciation and amortization	320,295	259,923	924,180	753,529
Other income (expense)	(7,668)	(3,832)	(34,537)	5,923
Fuel	177,677	182,415	519,772	515,065
Net income	883,240	810,391	1,605,751	1,495,339
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Net income	(3,447)	(745)	15,812	(5,157)
Gain (loss) on cash flow derivative hedges | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Net income	(3,253)	(373)	16,389	(4,071)
Gain (loss) on cash flow derivative hedges | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income | Interest rate swaps
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	(373)	(1,395)	(1,173)	(10,371)
Gain (loss) on cash flow derivative hedges | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income | Foreign currency forward contracts
Reclassifications out of accumulated other comprehensive loss
Depreciation and amortization	(3,592)	(3,157)	(10,471)	(9,625)
Other income (expense)	(1,251)	(835)	(3,866)	13,808
Gain (loss) on cash flow derivative hedges | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income | Fuel swaps
Reclassifications out of accumulated other comprehensive loss
Other income (expense)	(472)	466	(1,916)	658
Fuel	2,435	4,548	33,815	1,459
Actuarial loss | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Payroll and related	(194)	(372)	(577)	(1,086)
Changes in defined benefit plans | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Net income	$ (194)	$ (372)	$ (577)	$ (1,086)