CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING REVENUES:
Passenger	$ 3,126,708	$ 3,051,414	$ 3,030,023
Ground handling and other	77,560	69,792	65,540
Total operating revenues	3,204,268	3,121,206	3,095,563
OPERATING EXPENSES:
Salaries, wages and benefits	1,196,227	1,211,380	1,203,312
Aircraft maintenance, materials and repairs	579,463	569,306	604,863
Depreciation and amortization	292,768	284,969	264,507
Aircraft rentals	215,807	262,602	273,696
Aircraft fuel	162,653	122,284	118,124
Ground handling services	69,848	72,659	82,694
Special items		465,649
Other operating expenses	299,303	305,041	313,852
Total operating expenses	2,816,069	3,293,890	2,861,048
OPERATING INCOME (LOSS)	388,199	(172,684)	234,515
OTHER INCOME (EXPENSE):
Interest income	4,509	2,143	1,997
Interest expense	(104,925)	(78,177)	(75,850)
Other, net	400	(94)	33,660
Total other expense, net	(100,016)	(76,128)	(40,193)
INCOME (LOSS) BEFORE INCOME TAXES	288,183	(248,812)	194,322
PROVISION (BENEFIT) FOR INCOME TAXES	(140,724)	(87,226)	76,505
NET INCOME (LOSS)	$ 428,907	$ (161,586)	$ 117,817
BASIC EARNINGS (LOSS) PER SHARE (in dollars per share)	$ 8.28	$ (3.14)	$ 2.31
DILUTED EARNINGS (LOSS) PER SHARE (in dollars per share)	$ 8.08	$ (3.14)	$ 2.27
Weighted average common shares:
Basic (in shares)	51,804	51,505	51,077
Diluted (in shares)	53,100	51,505	51,825
COMPREHENSIVE INCOME (LOSS):
Net income (loss)	$ 428,907	$ (161,586)	$ 117,817
Net unrealized appreciation on marketable securities, net of taxes	21	189	29
TOTAL COMPREHENSIVE INCOME (LOSS)	$ 428,928	$ (161,397)	$ 117,846