Condensed Statements Of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities:
Net income	$ 110,078	$ 135,004
Adjustments to reconcile net income to net cash provided by operations:
Losses reclassified from other comprehensive income	167	178
Equity-based compensation	4,671	3,905
Allowance for doubtful accounts (recoveries)	(51)	221
Amortization of deferred gains and losses and debt issuance costs	4,761	2,810
Depreciation and amortization	66,840	48,066
Deferred income tax expense	64,789	45,810
Loss on disposal of assets	2,598	743
Lease termination costs	4,776	24,254
Changes in operating assets and liabilities:
Accounts receivable	(6,808)	(12,662)
Aircraft maintenance deposits	(17,940)	(29,721)
Prepaid income taxes	(1,598)	69,444
Long-term deposits and other assets	(44,900)	(22,055)
Accounts payable	16,388	3,024
Air traffic liability	105,486	66,531
Other liabilities	14,234	25,269
Other	239	0
Net cash provided by operating activities	323,730	360,821
Investing activities:
Purchase of available-for-sale investment securities	(68,459)	0
Proceeds from the maturity of available-for-sale investment securities	67,857	0
Proceeds from sale of property and equipment	0	50
Pre-delivery deposits for flight equipment, net of refunds	(79,357)	(60,772)
Capitalized interest	(6,375)	(4,554)
Purchase of property and equipment	(269,519)	(303,175)
Net cash used in investing activities	(355,853)	(368,451)
Financing activities:
Proceeds from issuance of long-term debt	255,827	300,547
Proceeds from stock options exercised	29	92
Payments on debt and capital lease obligations	(50,099)	(19,665)
Excess tax (deficiency) benefit from equity-based compensation	0	(511)
Repurchase of common stock	(1,217)	(62,278)
Debt issuance costs	(4,164)	(107)
Net cash provided by financing activities	200,376	218,078
Net (decrease) increase in cash and cash equivalents	168,253	210,448
Cash and cash equivalents at beginning of period	700,900	803,632
Cash and cash equivalents at end of period	869,153	1,014,080
Cash payments for:
Interest, net of capitalized interest	16,869	21,804
Income taxes paid, net of refunds	4,340	(36,142)
Non-cash transactions:
Capital expenditures funded by capital lease borrowings	$ (1,370)	$ (31)