Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
REVENUES	$ 1,452,183	$ 892,345	$ 1,068,200
OPERATING EXPENSES
Salaries, wages and benefits	433,518	300,514	276,106
Fuel	155,033	39,293	149,579
Maintenance, materials and repairs	170,151	146,692	141,575
Depreciation and amortization	257,532	178,895	154,556
Travel	90,993	34,443	27,390
Contracted ground and aviation services	64,076	16,640	147,092
Rent	16,006	13,899	13,629
Landing and ramp	11,184	5,968	22,271
Insurance	7,342	6,112	4,820
Transaction fees	373	5,264	0
Other operating expenses	68,978	33,607	31,782
Operating Expenses	1,275,186	781,327	968,800
OPERATING INCOME	176,997	111,018	99,400
OTHER INCOME (EXPENSE)
Interest income	370	251	116
Non-service component of retiree benefit costs	(9,404)	8,180	(6,105)
Non-service component of retiree benefit (costs) gains	(66,644)	(28,799)	(17,023)
Net gain (loss) on financial instruments	(12,302)	7,296	(79,789)
Other Nonoperating Income (Expense)	(105,425)	(23,540)	(105,936)
EARNINGS (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	71,572	87,478	(6,536)
INCOME TAX BENEFIT (EXPENSE)	(11,589)	(19,595)	28,276
EARNINGS FROM CONTINUING OPERATIONS	59,983	67,883	21,740
EARNINGS (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAXES	1,219	1,402	(3,245)
NET EARNINGS	$ 61,202	$ 69,285	$ 18,495
BASIC EARNINGS (LOSS) PER SHARE
Basic earnings per share from continuing operations (in dollars per share)	$ 1.02	$ 1.16	$ 0.37
Discontinued operations (in dollars per share)	0.02	0.02	(0.06)
TOTAL BASIC EARNINGS PER SHARE (in dollars per share)	1.04	1.18	0.31
DILUTED EARNINGS (LOSS) PER SHARE
Diluted earnings per share from continuing operations (in dollars per share)	0.78	0.89	0.36
Discontinued operations (in dollars per share)	0.01	0.02	(0.05)
TOTAL DILUTED NET EARNINGS PER SHARE (in dollars per share)	$ 0.79	$ 0.91	$ 0.31
WEIGHTED AVERAGE SHARES
Basic (in shares)	58,899	58,765	58,907
Diluted (in shares)	69,348	68,356	59,686