Condensed Consolidating Financial Information - Narrative and Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	$ 75,982	$ 755,151	$ 695,130	$ 2,124,091
Operating Expenses:
Wages and benefits	19,494	182,862	238,077	537,997
Aircraft fuel, including taxes and delivery	14,544	138,586	135,025	405,290
Maintenance, materials and repairs	18,664	61,363	93,067	182,539
Aircraft and passenger servicing	5,140	41,762	46,459	120,303
Commissions and other selling	5,201	33,291	34,844	96,598
Aircraft rent	26,230	30,534	77,120	91,773
Other rentals and landing fees	14,156	33,345	57,599	95,777
Depreciation and amortization	36,734	41,596	115,516	119,274
Purchased services	22,878	33,120	77,006	98,306
Special items	17,489	0	178,407	0
Other	16,525	42,056	80,143	118,041
Total	197,055	638,515	1,133,263	1,865,898
Operating Income (Loss)	(121,073)	116,636	(438,133)	258,193
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0	0	0
Other nonoperating special items	(7,011)	0	(7,011)	0
Interest expense and amortization of debt discounts and issuance costs	(11,596)	(6,438)	(26,612)	(21,268)
Interest income	1,942	3,148	7,728	9,205
Capitalized interest	831	1,171	2,583	3,713
Losses on fuel derivatives	(297)	(4,553)	(6,933)	(7,203)
Other, net	(6,380)	(1,445)	(2,915)	(5,553)
Total	(22,511)	(8,117)	(33,160)	(21,106)
Income (Loss) Before Income Taxes	(143,584)	108,519	(471,293)	237,087
Income tax benefit	(46,485)	28,443	(122,918)	62,820
Net Income (Loss)	(97,099)	80,076	(348,375)	174,267
Comprehensive Income (Loss)	(110,228)	83,050	(360,791)	177,294
Eliminations
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	(3,222)	(106)	(9,972)	(340)
Operating Expenses:
Wages and benefits	0	0	0	0
Aircraft fuel, including taxes and delivery	0	0	0	0
Maintenance, materials and repairs	(550)	0	(1,284)	0
Aircraft and passenger servicing	0	0	0	0
Commissions and other selling	(1)	(36)	(46)	(126)
Aircraft rent	0	0	0	0
Other rentals and landing fees	(28)	0	(82)	0
Depreciation and amortization	0	0	0	0
Purchased services	(2,641)	(16)	(8,548)	(47)
Special items	0		0
Other	(2)	(54)	(12)	(167)
Total	(3,222)	(106)	(9,972)	(340)
Operating Income (Loss)	0	0	0	0
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	95,952	(81,379)	344,832	(178,139)
Other nonoperating special items	0		0
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
Losses on fuel derivatives	0	0	0	0
Other, net	0	0	0	0
Total	95,952	(81,379)	344,832	(178,139)
Income (Loss) Before Income Taxes	95,952	(81,379)	344,832	(178,139)
Income tax benefit	0	0	0	0
Net Income (Loss)	95,952	(81,379)	344,832	(178,139)
Comprehensive Income (Loss)	109,081	(84,353)	357,248	(181,166)
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	(25)	0	(6)	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	39	70	189	194
Special items	0		0
Other	1,439	1,576	4,306	4,714
Total	1,453	1,646	4,489	4,919
Operating Income (Loss)	(1,453)	(1,646)	(4,489)	(4,919)
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	(95,952)	81,379	(344,832)	178,139
Other nonoperating special items	0		0
Interest expense and amortization of debt discounts and issuance costs	0	0	0	0
Interest income	1	4	4	25
Capitalized interest	0	0	0	0
Losses on fuel derivatives	0	0	0	0
Other, net	0	(8)	0	(8)
Total	(95,951)	81,375	(344,828)	178,156
Income (Loss) Before Income Taxes	(97,404)	79,729	(349,317)	173,237
Income tax benefit	(305)	(347)	(942)	(1,030)
Net Income (Loss)	(97,099)	80,076	(348,375)	174,267
Comprehensive Income (Loss)	(110,228)	83,050	(360,791)	177,294
Subsidiary Issuer / Guarantor | Reportable legal entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	76,090	754,608	694,755	2,122,368
Operating Expenses:
Wages and benefits	19,494	182,862	238,077	537,997
Aircraft fuel, including taxes and delivery	14,544	138,586	135,025	405,290
Maintenance, materials and repairs	18,027	58,056	89,992	176,131
Aircraft and passenger servicing	5,140	41,762	46,459	120,303
Commissions and other selling	5,221	33,310	34,833	96,655
Aircraft rent	26,182	30,365	77,128	91,564
Other rentals and landing fees	14,175	33,345	57,672	95,750
Depreciation and amortization	35,726	39,853	110,558	114,254
Purchased services	25,184	32,803	84,516	97,463
Special items	17,489		147,570
Other	14,503	40,099	74,178	112,159
Total	195,685	631,041	1,096,008	1,847,566
Operating Income (Loss)	(119,595)	123,567	(401,253)	274,802
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0	0	0
Other nonoperating special items	(7,011)		(7,011)
Interest expense and amortization of debt discounts and issuance costs	(11,596)	(6,438)	(26,612)	(21,252)
Interest income	1,941	3,144	7,724	9,180
Capitalized interest	831	1,171	2,583	3,713
Losses on fuel derivatives	(297)	(4,553)	(6,933)	(7,203)
Other, net	(6,380)	(1,437)	(2,910)	(5,538)
Total	(22,512)	(8,113)	(33,159)	(21,100)
Income (Loss) Before Income Taxes	(142,107)	115,454	(434,412)	253,702
Income tax benefit	(46,175)	29,899	(115,173)	66,309
Net Income (Loss)	(95,932)	85,555	(319,239)	187,393
Comprehensive Income (Loss)	(109,061)	88,529	(331,655)	190,420
Non-Guarantor Subsidiaries | Reportable legal entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	3,114	649	10,347	2,063
Operating Expenses:
Wages and benefits	0	0	0	0
Aircraft fuel, including taxes and delivery	0	0	0	0
Maintenance, materials and repairs	1,187	3,307	4,359	6,408
Aircraft and passenger servicing	0	0	0	0
Commissions and other selling	6	17	63	58
Aircraft rent	48	169	(8)	209
Other rentals and landing fees	9	0	9	27
Depreciation and amortization	1,008	1,743	4,958	5,020
Purchased services	296	263	849	696
Special items	0		30,837
Other	585	435	1,671	1,335
Total	3,139	5,934	42,738	13,753
Operating Income (Loss)	(25)	(5,285)	(32,391)	(11,690)
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0	0	0
Other nonoperating special items	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
Losses on fuel derivatives	0	0	0	0
Other, net	0	0	(5)	(7)
Total	0	0	(5)	(23)
Income (Loss) Before Income Taxes	(25)	(5,285)	(32,396)	(11,713)
Income tax benefit	(5)	(1,109)	(6,803)	(2,459)
Net Income (Loss)	(20)	(4,176)	(25,593)	(9,254)
Comprehensive Income (Loss)	$ (20)	$ (4,176)	$ (25,593)	$ (9,254)