CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING REVENUES:
Total operating revenues	$ 2,127,106	$ 2,971,963	$ 3,221,679
OPERATING EXPENSES:
Salaries, wages and benefits	826,109	1,001,746	1,201,518
Depreciation and amortization	474,959	368,098	334,589
CARES Act payroll support grant	(345,491)
Special items		21,869
Other operating expenses	222,797	243,729	272,826
Total operating expenses	2,018,304	2,459,705	2,747,399
OPERATING INCOME	108,802	512,258	474,280
OTHER INCOME (EXPENSE):
Interest income	5,879	14,131	8,823
Interest expense	(123,173)	(127,755)	(120,409)
Other, net	1,165	47,671	3,620
Total other expense, net	(116,129)	(65,953)	(107,966)
INCOME (LOSS) BEFORE INCOME TAXES	(7,327)	446,305	366,314
PROVISION FOR INCOME TAXES	1,188	106,206	85,942
NET INCOME (LOSS)	$ (8,515)	$ 340,099	$ 280,372
BASIC EARNINGS (LOSS) PER SHARE (in dollars per share)	$ (0.17)	$ 6.68	$ 5.40
DILUTED EARNINGS (LOSS) PER SHARE (in dollars per share)	$ (0.17)	$ 6.62	$ 5.30
Weighted average common shares:
Basic (in shares)	50,195,000	50,932,000	51,914,000
Diluted (in shares)	50,195,000	51,375,000	52,871,000
COMPREHENSIVE INCOME (LOSS):
Net income (loss)	$ (8,515)	$ 340,099	$ 280,372
Net unrealized appreciation on marketable securities, net of taxes		32	18
TOTAL COMPREHENSIVE INCOME (LOSS)	(8,515)	340,131	280,390
Flying agreements
OPERATING REVENUES:
Total operating revenues	2,060,801	2,889,265	3,169,520
Lease, airport services and other
OPERATING REVENUES:
Total operating revenues	66,305	82,698	52,159
Aircraft maintenance, materials and repairs
OPERATING EXPENSES:
Total operating expenses	618,989	514,313	556,259
Aircraft fuel
OPERATING EXPENSES:
Total operating expenses	61,739	119,115	117,657
Airport related expenses
OPERATING EXPENSES:
Total operating expenses	93,886	118,837	109,605
Aircraft rentals
OPERATING EXPENSES:
Total operating expenses	$ 65,316	$ 71,998	$ 154,945