CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 34,544	$ 35,206
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(508,562)	(109,900)
Sales of marketable securities	608,058	147,830
Proceeds from the sale of aircraft, property and equipment		2,966
Acquisition of property and equipment:
Aircraft and rotable spare parts	(94,941)	(258,795)
Buildings and ground equipment	(3,460)	(6,905)
Increase in other assets	(2,164)	(11,906)
NET CASH USED IN INVESTING ACTIVITIES	(1,069)	(236,710)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	68,232	203,083
Principal payments on long-term debt	(57,196)	(39,528)
Net proceeds from issuance of common stock	2,006	857
Increase in debt issuance cost	(747)	(2,028)
Payment of cash dividends	(2,040)	(2,047)
NET CASH PROVIDED BY FINANCING ACTIVITIES	10,255	160,337
Increase (decrease) in cash and cash equivalents	43,730	(41,167)
Cash and cash equivalents at beginning of period	203,035	132,275
CASH AND CASH EQUIVALENTS AT END OF PERIOD	246,765	91,108
Cash paid during the year for:
Interest, net of capitalized amounts	16,547	15,281
Income taxes	$ 684	$ 573