Condensed Consolidating Financial Information - Narrative and Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) pass_through_trust	Mar. 31, 2019 USD ($)
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	$ 559,144	$ 656,751
Operating Expenses:
Wages and benefits	188,254	175,065
Aircraft fuel, including taxes and delivery	113,478	126,104
Maintenance, materials and repairs	60,409	63,045
Aircraft and passenger servicing	38,283	38,900
Commissions and other selling	26,716	30,836
Aircraft rent	27,004	30,396
Other rentals and landing fees	29,766	31,046
Depreciation and amortization	39,449	38,151
Purchased services	34,241	32,453
Special items	126,904	0
Other	42,736	38,079
Total	727,240	604,075
Operating Loss	(168,096)	52,676
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0
Interest expense and amortization of debt discounts and issuance costs	(6,795)	(7,530)
Interest income	3,020	2,983
Capitalized interest	831	1,285
Gains (losses) on fuel derivatives	(6,452)	570
Other, net	2,304	(1,025)
Total	(7,092)	(3,717)
Income (Loss) Before Income Taxes	(175,188)	48,959
Income tax benefit	(30,816)	12,601
Net Income (Loss)	(144,372)	36,358
Comprehensive Income (Loss)	(143,041)	38,619
Eliminations
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	(3,908)	(131)
Operating Expenses:
Wages and benefits	0	0
Aircraft fuel, including taxes and delivery	0	0
Maintenance, materials and repairs	(554)	0
Aircraft and passenger servicing	0	0
Commissions and other selling	(45)	(47)
Aircraft rent	0	0
Other rentals and landing fees	(27)	0
Depreciation and amortization	0	0
Purchased services	(3,266)	(16)
Special items	0
Other	(16)	(68)
Total	(3,908)	(131)
Operating Loss	0	0
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	143,225	(37,849)
Interest expense and amortization of debt discounts and issuance costs	0	0
Interest income	0	0
Capitalized interest	0	0
Gains (losses) on fuel derivatives	0	0
Other, net	0	0
Total	143,225	(37,849)
Income (Loss) Before Income Taxes	143,225	(37,849)
Income tax benefit	0	0
Net Income (Loss)	143,225	(37,849)
Comprehensive Income (Loss)	141,894	(40,110)
Parent Issuer / Guarantor
Operating Expenses:
Special items	0
Parent Issuer / Guarantor | Reportable Legal Entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	0	0
Operating Expenses:
Wages and benefits	0	0
Aircraft fuel, including taxes and delivery	0	0
Maintenance, materials and repairs	0	0
Aircraft and passenger servicing	0	0
Commissions and other selling	19	0
Aircraft rent	0	0
Other rentals and landing fees	0	0
Depreciation and amortization	0	0
Purchased services	90	54
Other	1,346	1,842
Total	1,455	1,896
Operating Loss	(1,455)	(1,896)
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	(143,225)	37,849
Interest expense and amortization of debt discounts and issuance costs	0	0
Interest income	3	8
Capitalized interest	0	0
Gains (losses) on fuel derivatives	0	0
Other, net	0	0
Total	(143,222)	37,857
Income (Loss) Before Income Taxes	(144,677)	35,961
Income tax benefit	(305)	(397)
Net Income (Loss)	(144,372)	36,358
Comprehensive Income (Loss)	$ (143,041)	38,619
Subsidiary Issuer / Guarantor
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Number of pass-through trusts | pass_through_trust	2
Operating Expenses:
Special items	$ 126,904
Subsidiary Issuer / Guarantor | Reportable Legal Entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	559,162	656,090
Operating Expenses:
Wages and benefits	188,254	175,065
Aircraft fuel, including taxes and delivery	113,478	126,104
Maintenance, materials and repairs	59,066	61,802
Aircraft and passenger servicing	38,283	38,900
Commissions and other selling	26,700	30,865
Aircraft rent	27,023	30,367
Other rentals and landing fees	29,793	31,019
Depreciation and amortization	37,477	36,492
Purchased services	37,096	32,193
Other	40,732	35,856
Total	724,806	598,663
Operating Loss	(165,644)	57,427
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0
Interest expense and amortization of debt discounts and issuance costs	(6,795)	(7,514)
Interest income	3,017	2,975
Capitalized interest	831	1,285
Gains (losses) on fuel derivatives	(6,452)	570
Other, net	2,305	(1,069)
Total	(7,094)	(3,753)
Income (Loss) Before Income Taxes	(172,738)	53,674
Income tax benefit	(30,301)	13,591
Net Income (Loss)	(142,437)	40,083
Comprehensive Income (Loss)	(141,106)	42,344
Non-Guarantor Subsidiaries
Operating Expenses:
Special items	0
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	3,890	792
Operating Expenses:
Wages and benefits	0	0
Aircraft fuel, including taxes and delivery	0	0
Maintenance, materials and repairs	1,897	1,243
Aircraft and passenger servicing	0	0
Commissions and other selling	42	18
Aircraft rent	(19)	29
Other rentals and landing fees	0	27
Depreciation and amortization	1,972	1,659
Purchased services	321	222
Other	674	449
Total	4,887	3,647
Operating Loss	(997)	(2,855)
Nonoperating Income (Expense):
Undistributed net loss of subsidiaries	0	0
Interest expense and amortization of debt discounts and issuance costs	0	(16)
Interest income	0	0
Capitalized interest	0	0
Gains (losses) on fuel derivatives	0	0
Other, net	(1)	44
Total	(1)	28
Income (Loss) Before Income Taxes	(998)	(2,827)
Income tax benefit	(210)	(593)
Net Income (Loss)	(788)	(2,234)
Comprehensive Income (Loss)	$ (788)	$ (2,234)