Condensed Consolidating Financial Information - Narrative and Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) pass_through_trust	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) pass_through_trust	Jun. 30, 2019 USD ($)
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	$ 60,004	$ 712,189	$ 619,148	$ 1,368,940
Operating Expenses:
Wages and benefits	30,329	180,070	218,583	355,135
Aircraft fuel, including taxes and delivery	7,003	140,600	120,481	266,704
Maintenance, materials and repairs	13,994	58,131	74,403	121,176
Aircraft and passenger servicing	3,036	39,641	41,319	78,541
Commissions and other selling	2,927	32,471	29,643	63,307
Aircraft rent	23,886	30,843	50,890	61,239
Other rentals and landing fees	13,677	31,386	43,443	62,432
Depreciation and amortization	39,333	39,527	78,782	77,678
Purchased services	19,887	32,733	54,128	65,186
Special items	34,014	0	160,918	0
Other	20,882	37,906	63,618	75,985
Total	208,968	623,308	936,208	1,227,383
Operating Income (Loss)	(148,964)	88,881	(317,060)	141,557
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0	0	0
Interest expense and amortization of debt discounts and issuance costs	(8,221)	(7,300)	(15,016)	(14,830)
Interest income	2,766	3,074	5,786	6,057
Capitalized interest	921	1,257	1,752	2,542
Gains (losses) on fuel derivatives	(184)	(3,220)	(6,636)	(2,650)
Other, net	1,161	(3,083)	3,465	(4,108)
Total	(3,557)	(9,272)	(10,649)	(12,989)
Income (Loss) Before Income Taxes	(152,521)	79,609	(327,709)	128,568
Income tax benefit	(45,617)	21,776	(76,433)	34,377
Net Income (Loss)	(106,904)	57,833	(251,276)	94,191
Comprehensive Income (Loss)	(107,522)	55,625	(250,563)	94,244
Eliminations
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	(2,842)	(103)	(6,750)	(234)
Operating Expenses:
Wages and benefits	0	0	0	0
Aircraft fuel, including taxes and delivery	0	0	0	0
Maintenance, materials and repairs	(180)	0	(734)	0
Aircraft and passenger servicing	0	0	0	0
Commissions and other selling	0	(43)	(45)	(90)
Aircraft rent	0	0	0	0
Other rentals and landing fees	(27)	0	(54)	0
Depreciation and amortization	0	0	0	0
Purchased services	(2,641)	(15)	(5,907)	(31)
Special items	0		0
Other	6	(45)	(10)	(113)
Total	(2,842)	(103)	(6,750)	(234)
Operating Income (Loss)	0	0	0	0
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	105,651	(58,911)	248,880	(96,760)
Interest expense and amortization of debt discounts and issuance costs	0	0	0	0
Interest income	0	0	0	0
Capitalized interest	0	0	0	0
Gains (losses) on fuel derivatives	0	0	0	0
Other, net	0	0	0	0
Total	105,651	(58,911)	248,880	(96,760)
Income (Loss) Before Income Taxes	105,651	(58,911)	248,880	(96,760)
Income tax benefit	0	0	0	0
Net Income (Loss)	105,651	(58,911)	248,880	(96,760)
Comprehensive Income (Loss)	106,269	(56,703)	248,167	(96,813)
Parent Issuer / Guarantor
Operating Expenses:
Special items	0		0
Parent Issuer / Guarantor | Reportable Legal Entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	0	0	0	0
Operating Expenses:
Wages and benefits	0	0	0	0
Aircraft fuel, including taxes and delivery	0	0	0	0
Maintenance, materials and repairs	0	0	0	0
Aircraft and passenger servicing	0	0	0	0
Commissions and other selling	0	11	19	11
Aircraft rent	0	0	0	0
Other rentals and landing fees	0	0	0	0
Depreciation and amortization	0	0	0	0
Purchased services	60	70	150	124
Other	1,521	1,296	2,867	3,138
Total	1,581	1,377	3,036	3,273
Operating Income (Loss)	(1,581)	(1,377)	(3,036)	(3,273)
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	(105,651)	58,911	(248,880)	96,760
Interest expense and amortization of debt discounts and issuance costs	0	0	0	0
Interest income	0	13	3	21
Capitalized interest	0	0	0	0
Gains (losses) on fuel derivatives	0	0	0	0
Other, net	(4)	0	0	0
Total	(105,655)	58,924	(248,877)	96,781
Income (Loss) Before Income Taxes	(107,236)	57,547	(251,913)	93,508
Income tax benefit	(332)	(286)	(637)	(683)
Net Income (Loss)	(106,904)	57,833	(251,276)	94,191
Comprehensive Income (Loss)	$ (107,522)	55,625	$ (250,563)	94,244
Subsidiary Issuer / Guarantor
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Number of pass-through trusts | pass_through_trust	2		2
Operating Expenses:
Special items	$ 3,177		$ 130,081
Subsidiary Issuer / Guarantor | Reportable Legal Entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	59,503	711,670	618,665	1,367,760
Operating Expenses:
Wages and benefits	30,329	180,070	218,583	355,135
Aircraft fuel, including taxes and delivery	7,003	140,600	120,481	266,704
Maintenance, materials and repairs	12,899	56,273	71,965	118,075
Aircraft and passenger servicing	3,036	39,641	41,319	78,541
Commissions and other selling	2,912	32,480	29,612	63,345
Aircraft rent	23,923	30,832	50,946	61,199
Other rentals and landing fees	13,704	31,386	43,497	62,405
Depreciation and amortization	37,355	37,909	74,832	74,401
Purchased services	22,236	32,467	59,332	64,660
Other	18,943	36,204	59,675	72,060
Total	175,517	617,862	900,323	1,216,525
Operating Income (Loss)	(116,014)	93,808	(281,658)	151,235
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0	0	0
Interest expense and amortization of debt discounts and issuance costs	(8,221)	(7,300)	(15,016)	(14,814)
Interest income	2,766	3,061	5,783	6,036
Capitalized interest	921	1,257	1,752	2,542
Gains (losses) on fuel derivatives	(184)	(3,220)	(6,636)	(2,650)
Other, net	1,165	(3,032)	3,470	(4,101)
Total	(3,553)	(9,234)	(10,647)	(12,987)
Income (Loss) Before Income Taxes	(119,567)	84,574	(292,305)	138,248
Income tax benefit	(38,697)	22,819	(68,998)	36,410
Net Income (Loss)	(80,870)	61,755	(223,307)	101,838
Comprehensive Income (Loss)	(81,488)	59,547	(222,594)	101,891
Non-Guarantor Subsidiaries
Operating Expenses:
Special items	30,837		30,837
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	3,343	622	7,233	1,414
Operating Expenses:
Wages and benefits	0	0	0	0
Aircraft fuel, including taxes and delivery	0	0	0	0
Maintenance, materials and repairs	1,275	1,858	3,172	3,101
Aircraft and passenger servicing	0	0	0	0
Commissions and other selling	15	23	57	41
Aircraft rent	(37)	11	(56)	40
Other rentals and landing fees	0	0	0	27
Depreciation and amortization	1,978	1,618	3,950	3,277
Purchased services	232	211	553	433
Other	412	451	1,086	900
Total	34,712	4,172	39,599	7,819
Operating Income (Loss)	(31,369)	(3,550)	(32,366)	(6,405)
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0	0	0
Interest expense and amortization of debt discounts and issuance costs	0	0		(16)
Interest income	0	0	0	0
Capitalized interest	0	0	0	0
Gains (losses) on fuel derivatives	0	0	0	0
Other, net	0	(51)	(5)	(7)
Total	0	(51)	(5)	(23)
Income (Loss) Before Income Taxes	(31,369)	(3,601)	(32,371)	(6,428)
Income tax benefit	(6,588)	(757)	(6,798)	(1,350)
Net Income (Loss)	(24,781)	(2,844)	(25,573)	(5,078)
Comprehensive Income (Loss)	$ (24,781)	$ (2,844)	$ (25,573)	$ (5,078)