Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Revenue:
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
Depreciation and amortization	36,734			41,596			115,516	119,274
Aircraft rent	26,230			30,534			77,120	91,773
Commissions and other selling	5,201			33,291			34,844	96,598
Other rentals and landing fees	14,156			33,345			57,599	95,777
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):
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)
Losses on fuel derivatives	(297)			(4,553)			(6,933)	(7,203)
Interest income	1,942			3,148			7,728	9,205
Capitalized interest	831			1,171			2,583	3,713
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 expense (benefit)	(46,485)			28,443			(122,918)	62,820
Net Income (Loss)	$ (97,099)	$ (106,904)	$ (144,372)	$ 80,076	$ 57,833	$ 36,358	$ (348,375)	$ 174,267
Net Income (Loss) Per Share
Basic (in dollars per share)	$ (2.11)			$ 1.70			$ (7.58)	$ 3.65
Diluted (in dollars per share)	$ (2.11)			$ 1.70			$ (7.58)	$ 3.64
Weighted Average Number of Common Stock Shares Outstanding:
Basic (in shares)	46,001			47,119			45,980	47,784
Diluted (in shares)	46,001			47,236			45,980	47,847
Cash dividend declared per common stock share (in dollars per share)	$ 0		$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.36
Passenger
Operating Revenue:
Operating revenue	$ 39,777			$ 694,263			$ 573,008	$ 1,948,990
Other
Operating Revenue:
Operating revenue	$ 36,205			$ 60,888			$ 122,122	$ 175,101