Condensed Statements Of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net income	$ 170,268	$ 216,386
Adjustments to reconcile net income to net cash provided by operations:
Losses reclassified from other comprehensive income	252	267
Equity-based compensation	6,723	5,503
Allowance for doubtful accounts (recoveries)	(53)	213
Amortization of deferred gains and losses and debt issuance costs	6,415	3,837
Depreciation and amortization	103,680	73,370
Deferred income tax expense	97,834	77,627
Loss on disposal of assets	3,114	1,166
Lease termination costs	12,629	31,609
Changes in operating assets and liabilities:
Accounts receivable	(5,046)	(7,840)
Aircraft maintenance deposits, net	(28,422)	(38,299)
Prepaid income taxes	(160)	66,218
Long-term deposits and other assets	(81,622)	(43,252)
Accounts payable	13,829	(7,044)
Air traffic liability	70,540	21,963
Other liabilities	16,152	38,317
Other	339	0
Net cash provided by operating activities	386,472	440,041
Investing activities:
Purchase of available-for-sale investment securities	(96,851)	(100,076)
Proceeds from the maturity of available-for-sale investment securities	95,881	0
Proceeds from sale of property and equipment	0	50
Pre-delivery deposits for flight equipment, net of refunds	(121,702)	(109,260)
Capitalized interest	(8,054)	(7,032)
Purchase of property and equipment	(428,061)	(447,455)
Net cash used in investing activities	(558,787)	(663,773)
Financing activities:
Proceeds from issuance of long-term debt	405,827	378,569
Proceeds from stock options exercised	45	92
Payments on debt and capital lease obligations	(63,643)	(29,663)
Excess tax (deficiency) benefit from equity-based compensation	0	(497)
Repurchase of common stock	(1,238)	(102,390)
Debt issuance costs	(5,896)	(107)
Net cash provided by financing activities	335,095	246,004
Net (decrease) increase in cash and cash equivalents	162,780	22,272
Cash and cash equivalents at beginning of period	700,900	803,632
Cash and cash equivalents at end of period	863,680	825,904
Cash payments for:
Interest, net of capitalized interest	22,541	26,025
Income taxes paid, net of refunds	4,352	(18,169)
Non-cash transactions:
Capital expenditures funded by capital lease borrowings	$ (1,370)	$ (31)