CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
OPERATING REVENUES:
Total operating revenues	$ 723,694	$ 783,400
OPERATING EXPENSES:
Salaries, wages and benefits	257,588	306,719
Depreciation and amortization	89,986	77,585
Special items	21,869
Other operating expenses	63,109	68,389
Total operating expenses	627,275	695,225
OPERATING INCOME	96,419	88,175
OTHER INCOME (EXPENSE):
Interest income	3,807	1,705
Interest expense	(32,507)	(26,234)
Other income (expense), net	46,725	3,558
Total other expense, net	18,025	(20,971)
INCOME BEFORE INCOME TAXES	114,444	67,204
PROVISION FOR INCOME TAXES	26,263	12,842
NET INCOME	$ 88,181	$ 54,362
BASIC EARNINGS PER SHARE (in dollars per share)	$ 1.71	$ 1.05
DILUTED EARNINGS PER SHARE (in dollars per share)	$ 1.69	$ 1.03
Weighted average common shares:
Basic (in shares)	51,440	51,921
Diluted (in shares)	52,098	53,033
COMPREHENSIVE INCOME:
Net income	$ 88,181	$ 54,362
Net unrealized appreciation (depreciation) on debt securities, net of taxes	32	(50)
TOTAL COMPREHENSIVE INCOME	88,213	54,312
Flying agreements
OPERATING REVENUES:
Total operating revenues	700,001	767,964
Airport customer service and other
OPERATING REVENUES:
Total operating revenues	23,693	15,436
Aircraft maintenance, materials and repairs
OPERATING EXPENSES:
Total operating expenses	118,262	141,606
Airport related expenses
OPERATING EXPENSES:
Total operating expenses	30,647	29,307
Aircraft fuel
OPERATING EXPENSES:
Total operating expenses	25,656	26,939
Aircraft rentals
OPERATING REVENUES:
Total operating revenues	207,381	189,068
OPERATING EXPENSES:
Total operating expenses	$ 20,158	$ 44,680