Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Amounts reclassified from AOCI
Passenger revenue	$ (60,004)		$ (712,189)		$ (619,148)	$ (1,368,940)
Nonoperating Income (Expense), Other, net	(1,161)		3,083		(3,465)	4,108
Total before tax	152,521		(79,609)		327,709	(128,568)
Tax expense	(45,617)		21,776		(76,433)	34,377
Total, net of tax	106,904		(57,833)		251,276	(94,191)
Net income	106,904	$ 144,372	(57,833)	$ (36,358)	251,276	(94,191)
Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Net income	(2,216)		(602)		(4,405)	(1,152)
Derivative instruments under ASC 815 | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Total before tax	(3,538)		(1,749)		(7,438)	(3,336)
Tax expense	875		426		1,840	817
Total, net of tax	(2,663)		(1,323)		(5,598)	(2,519)
Defined benefit plan | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Total before tax	978		887		1,956	1,774
Tax expense	(242)		(218)		(484)	(386)
Total, net of tax	736		669		1,472	1,388
Actuarial loss | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Nonoperating Income (Expense), Other, net	922		831		1,844	1,662
Prior service cost | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Nonoperating Income (Expense), Other, net	56		56		112	112
Short-term investments | Amount reclassified from accumulated other comprehensive income (loss)
Amounts reclassified from AOCI
Realized losses (gain) on sales of investments, net	(384)		69		(371)	(28)
Total before tax	(384)		69		(371)	(28)
Tax expense	95		(17)		92	7
Total, net of tax	(289)		52		(279)	(21)
Passenger
Amounts reclassified from AOCI
Passenger revenue	(29,762)		(653,423)		(533,231)	(1,254,727)
Passenger | Derivative instruments under ASC 815 | Amount reclassified from accumulated other comprehensive income (loss) | Foreign currency derivative gains, net
Amounts reclassified from AOCI
Passenger revenue	(1,961)		(1,749)		(3,075)	(3,336)
Nonoperating Income (Expense), Other, net	$ 1,577		$ 0		$ 4,363	$ 0