Condensed Statements Of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities:
Net income (loss)	$ (33,668)	$ 108,502
Adjustments to reconcile net income (loss) to net cash provided by operations:
Losses reclassified from other comprehensive income	159	167
Stock-based compensation	5,381	4,671
Allowance for doubtful accounts (recoveries)	(12)	(51)
Amortization of deferred gains and losses and debt issuance costs	4,552	4,761
Depreciation and amortization	84,991	66,840
Deferred income tax expense (benefit)	(17,604)	64,789
Loss on disposal of assets	5,492	2,598
Lease termination costs	0	4,776
Special charges, non-operating	88,613	0
Changes in operating assets and liabilities:
Accounts receivable	(9,212)	(6,808)
Aircraft maintenance deposits, net	11,222	(17,940)
Prepaid income taxes	0	(1,598)
Long-term deposits and other assets	3,003	(17,507)
Deferred heavy maintenance	(94,267)	(28,191)
Income tax receivable	(828)	0
Accounts payable	25,413	16,387
Air traffic liability	93,936	108,574
Other liabilities	83,809	13,518
Other	8	239
Net cash provided by operating activities	250,988	323,727
Investing activities:
Purchase of available-for-sale investment securities	(73,687)	(68,459)
Proceeds from the maturity of available-for-sale investment securities	72,964	67,857
Proceeds from sale of property and equipment	9,500	0
Pre-delivery deposits for flight equipment, net of refunds	(92,205)	(79,357)
Capitalized interest	(4,178)	(6,375)
Purchase of property and equipment	(323,229)	(269,519)
Net cash used in investing activities	(410,835)	(355,853)
Financing activities:
Proceeds from issuance of long-term debt	440,340	255,827
Proceeds from stock options exercised	2	29
Payments on debt obligations	(60,649)	(49,980)
Payments on capital lease obligations	(205,403)	(119)
Repurchase of common stock	(986)	(1,217)
Debt issuance costs	(1,944)	(4,164)
Net cash provided by financing activities	171,360	200,376
Net (decrease) increase in cash and cash equivalents	11,513	168,250
Cash and cash equivalents at beginning of period	800,849	700,900
Cash and cash equivalents at end of period	812,362	869,150
Cash payments for:
Interest, net of capitalized interest	16,769	16,869
Income taxes paid, net of refunds	3,270	4,340
Non-cash transactions:
Capital expenditures funded by capital lease borrowings	$ (315)	$ (1,370)