Changes in Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	$ 111,304	$ 81,864	$ 211,719	$ 149,742
Depreciation and amortization	311,600	253,376	603,885	493,606
Other income (expense)	(21,781)	33,855	(26,869)	9,755
Fuel	181,924	172,309	342,095	332,650
Other operating	(93,698)	9,400	(155,723)	(46,093)
Net income	472,830	466,295	722,511	684,948
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Net income	6,725	10,845	19,259	(4,412)
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	6,920	11,217	19,642	(3,698)
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	(409)	(2,138)	(800)	(8,976)
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	(3,545)	(3,156)	(6,879)	(6,468)
Other income (expense)	(1,300)	14,601	(2,615)	14,643
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)	(1,188)	(133)	(1,444)	192
Fuel	13,362	2,043	31,380	(3,089)
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	(195)	(372)	(383)	(714)
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	(195)	(372)	(383)	(714)
Foreign cumulative translation | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Other operating	$ 0	$ 0	$ 0	$ 0