CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 143,933	$ 34,544
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(455,990)	(508,562)
Sales of marketable securities	383,163	608,058
Proceeds from the sale of aircraft, property and equipment	36,512
Acquisition of property and equipment:
Aircraft and rotable spare parts	(220,916)	(94,941)
Buildings and ground equipment	(479)	(3,460)
Aircraft deposits applied towards acquired aircraft	11,228
Increase in other assets	(2,425)	(2,164)
NET CASH USED IN INVESTING ACTIVITIES	(248,907)	(1,069)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	157,983	68,232
Principal payments on long-term debt	(88,104)	(57,196)
Net proceeds from issuance of common stock	1,481	2,006
Purchase of treasury stock	(13,671)
Increase in debt issuance cost	(1,452)	(747)
Payment of cash dividends	(2,588)	(2,040)
NET CASH PROVIDED BY FINANCING ACTIVITIES	53,649	10,255
Decrease in cash and cash equivalents	(51,325)	43,730
Cash and cash equivalents at beginning of period	146,766	203,035
CASH AND CASH EQUIVALENTS AT END OF PERIOD	95,441	246,765
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Acquisition of rotable spare parts	1,704
Cash paid during the period for:
Interest, net of capitalized amounts	24,039	16,547
Income taxes	$ 478	$ 684