CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 228,034	$ 168,807
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(1,061,392)	(337,375)
Sales of marketable securities	1,071,668	430,688
Proceeds from the sale of aircraft, property and equipment		5,719
Acquisition of property and equipment:
Aircraft and rotable spare parts	(314,657)	(503,317)
Buildings and ground equipment	(7,303)	(16,842)
Return of deposits on aircraft		2,300
Increase in other assets	(1,499)	(4,883)
NET CASH USED IN INVESTING ACTIVITIES	(313,183)	(423,710)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	248,966	432,568
Principal payments on long-term debt	(136,328)	(114,202)
Net proceeds from issuance of common stock	4,048	1,709
Purchase of treasury stock		(18,726)
Increase in debt issuance cost	(2,495)	(3,442)
Payment of cash dividends	(4,095)	(4,114)
NET CASH PROVIDED BY FINANCING ACTIVITIES	110,096	293,793
Increase in cash and cash equivalents	24,947	38,890
Cash and cash equivalents at beginning of period	203,035	132,275
CASH AND CASH EQUIVALENTS AT END OF PERIOD	227,982	171,165
Cash paid during the year for:
Interest, net of capitalized amounts	35,887	37,530
Income taxes	$ 741	$ 613