CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 109,347	$ 51,324
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(222,616)	(234,342)
Sales of marketable securities	219,362	382,351
Proceeds from the sale of equipment	630	191
Acquisition of property and equipment:
Aircraft and rotable spare parts	(27,555)	(29,029)
Deposits on aircraft		(13,500)
Buildings and ground equipment	(3,252)	(5,009)
Increase in other assets	(9,397)	(3,850)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(42,828)	96,812
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on long-term debt	(84,598)	(79,363)
Tax benefit from exercise of common stock options	73	2
Return of deposits on aircraft and rotable spare parts		400
Net proceeds from issuance of common stock	2,161	2,203
Purchase of treasury stock	(897)	(40,259)
Payment of cash dividends	(4,070)	(4,326)
NET CASH USED IN FINANCING ACTIVITIES	(87,331)	(121,343)
Increase (decrease) in cash and cash equivalents	(20,812)	26,793
Cash and cash equivalents at beginning of period	129,526	112,338
CASH AND CASH EQUIVALENTS AT END OF PERIOD	108,714	139,131
Cash paid (received) during the year for:
Interest, net of capitalized amounts	39,261	41,370
Income taxes	$ (1,477)	$ 698