Changes in Accumulated Other Comprehensive (Loss) Income - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	$ 81,864	$ 76,632	$ 149,742	$ 156,949
Depreciation and amortization	253,376	234,937	493,606	470,686
Other income (expense)	9,400	(50,171)	(46,093)	(114,967)
Fuel	172,309	170,748	332,650	348,162
Net income	466,295	369,526	684,948	584,252
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income
Reclassifications out of accumulated other comprehensive loss
Net income	10,845	(54,910)	(4,412)	(108,564)
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	11,217	(54,617)	(3,698)	(108,007)
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	(2,138)	(7,863)	(8,976)	(16,720)
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	(3,156)	(2,710)	(6,468)	(5,420)
Other income (expense)	14,601	(4,105)	14,643	(7,675)
Loss on cash flow derivative hedges | Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income | Foreign currency collar options
Reclassifications out of accumulated other comprehensive loss
Depreciation and amortization	0	(602)	0	(1,204)
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)	(133)	2,498	192	4,775
Fuel	2,043	(41,835)	(3,089)	(81,763)
Actuarial loss
Reclassifications out of accumulated other comprehensive loss
Net income	(372)	(293)	(714)	(557)
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	$ (372)	$ (293)	$ (714)	$ (557)