Condensed Statements Of Cash Flows (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement of Cash Flows [Abstract]
Net cash provided by operating activities	$ 85,193	$ 79,674
Investing activities:
Pre-delivery deposits for flight equipment, net of refunds	(15,127)	(409)
Purchase of property and equipment	(10,588)	(7,970)
Net cash used in investing activities	(25,715)	(8,379)
Financing activities:
Proceeds from options exercised	449	213
Proceeds from sale leaseback transactions	6,900	5,627
Excess tax benefits from share-based compensation	162	825
Repurchase of common stock	(321)	(457)
Net cash provided by financing activities	7,190	6,208
Net increase in cash and cash equivalents	66,668	77,503
Cash and cash equivalents at beginning of period	416,816	343,328
Cash and cash equivalents at end of period	483,484	420,831
Cash payments for:
Interest	9	12
Taxes	$ 932	$ 1,486