Changes in Accumulated Other Comprehensive (Loss) Income - Reclassifications (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	$ (70,159)	$ (68,571)
Depreciation and amortization expenses	(200,468)	(193,735)
Other income (expense)	(60,452)	(71,009)
Fuel	(205,276)	(244,459)
Net income	45,230	26,457
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income
Reclassifications out of accumulated other comprehensive loss
Net income	(55,211)	(4,868)
Loss on cash flow derivative hedges: | Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income
Reclassifications out of accumulated other comprehensive loss
Net income	(54,648)	(4,437)
Loss on cash flow derivative hedges: | Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income | Cross currency swaps
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	0	(261)
Loss on cash flow derivative hedges: | Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income | Foreign currency forward contracts
Reclassifications out of accumulated other comprehensive loss
Interest expense, net of interest capitalized	0	(57)
Depreciation and amortization expenses	(718)	(449)
Other income (expense)	(238)	(3,576)
Loss on cash flow derivative hedges: | Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income | Fuel swaps
Reclassifications out of accumulated other comprehensive loss
Fuel	(53,692)	(94)
Amortization of defined benefit plans: | Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income
Reclassifications out of accumulated other comprehensive loss
Actuarial loss	(354)	(222)
Prior service costs	(209)	(209)
Net income	$ (563)	$ (431)