CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
OPERATING REVENUES:
Total operating revenues	$ 829,275	$ 812,673	[1]	$ 2,418,190	$ 2,351,351
OPERATING EXPENSES:
Salaries, wages and benefits	301,378	304,014	[1]	901,775	896,476
Depreciation and amortization	86,088	74,095	[1]	246,386	215,415
Other operating expenses	68,859	65,432	[1]	206,511	190,235
Total operating expenses	691,350	700,304	[1]	2,065,412	2,056,092
OPERATING INCOME	137,925	112,369	[1]	352,778	295,259
OTHER INCOME (EXPENSE):
Interest income	2,283	1,408	[1]	5,692	3,398
Interest expense	(31,440)	(27,101)	[1]	(86,485)	(78,713)
Other income (expense), net	1,157			3,470
Total other expense, net	(28,000)	(25,693)	[1]	(77,323)	(75,315)
INCOME BEFORE INCOME TAXES	109,925	86,676	[1]	275,455	219,944
PROVISION FOR INCOME TAXES	26,879	32,960	[1]	62,189	80,966
NET INCOME	$ 83,046	$ 53,716	[1]	$ 213,266	$ 138,978
BASIC EARNINGS PER SHARE (in dollars per share)	$ 1.60	$ 1.04	[1]	$ 4.10	$ 2.68
DILUTED EARNINGS PER SHARE (in dollars per share)	$ 1.57	$ 1.01	[1]	$ 4.03	$ 2.62
Weighted average common shares:
Basic (in shares)	52,039	51,833	[1]	52,002	51,801
Diluted (in shares)	52,981	53,080	[1]	52,976	53,087
COMPREHENSIVE INCOME:
Net income	$ 83,046	$ 53,716	[1]	$ 213,266	$ 138,978
Net unrealized appreciation (depreciation) on marketable securities, net of taxes	(2)	11	[1]	32	67
TOTAL COMPREHENSIVE INCOME	83,044	53,727	[1]	213,298	139,045
Flying agreements
OPERATING REVENUES:
Total operating revenues	816,057	800,965	[1]	2,377,659	2,317,218
Airport customer service and other
OPERATING REVENUES:
Total operating revenues	13,218	11,708	[1]	40,531	34,133
Aircraft maintenance, materials and repairs
OPERATING EXPENSES:
Total operating expenses	142,285	148,787	[1]	423,665	433,467
Aircraft rentals
OPERATING REVENUES:
Total operating revenues	208,813	213,967		599,188	621,099
OPERATING EXPENSES:
Total operating expenses	36,827	54,976	[1]	119,015	168,098
Aircraft fuel
OPERATING EXPENSES:
Other operating expenses		22,791			61,295
Total operating expenses	25,655	30,209	[1]	80,852	91,106
Airport related expenses
OPERATING EXPENSES:
Other operating expenses		30,209			91,106
Total operating expenses	$ 30,258	$ 22,791	[1]	$ 87,208	$ 61,295

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.