Condensed Consolidating Financial Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	$ 639,462	$ 599,298	$ 1,740,040	$ 1,623,980
Operating Expenses:
Aircraft fuel, including taxes and delivery	182,219	181,334	527,497	525,046
Wages and benefits	114,469	112,150	334,441	318,269
Aircraft rent	26,724	27,575	79,098	81,879
Maintenance materials and repairs	51,293	51,705	168,002	160,000
Aircraft and passenger servicing	31,848	31,080	92,929	89,367
Commissions and other selling	32,015	32,288	94,123	98,285
Depreciation and amortization	24,384	22,092	70,960	60,993
Other rentals and landing fees	23,637	21,996	65,855	60,773
Other	46,704	44,644	139,335	129,469
Total	533,293	524,864	1,572,240	1,524,081
Operating Income	106,169	74,434	167,800	99,899
Nonoperating Income (Expense):
Interest expense and amortization of debt discounts and issuance costs	(17,104)	(13,479)	(48,111)	(37,019)
Interest income	471	173	1,088	426
Capitalized interest	1,834	3,005	6,584	9,336
Gains (losses) on fuel derivatives	(27,892)	2,536	(28,506)	(10,931)
Other, net	(5,114)	749	(3,804)	(3,457)
Total	(47,805)	(7,016)	(72,749)	(41,645)
Income Before Income Taxes	58,364	67,418	95,051	58,254
Income tax expense	22,789	26,814	37,224	23,479
Net Income	35,575	40,604	57,827	34,775
Comprehensive Income (Loss)	42,610	37,520	56,435	41,113
Parent Issuer / Guarantor
Operating Expenses:
Other rentals and landing fees	5	0	5	0
Other	1,246	1,072	4,015	6,557
Total	1,251	1,072	4,020	6,557
Operating Income	(1,251)	(1,072)	(4,020)	(6,557)
Nonoperating Income (Expense):
Undistributed net income of subsidiaries	37,900	42,686	64,787	43,310
Interest expense and amortization of debt discounts and issuance costs	(2,260)	(2,207)	(6,650)	(6,475)
Interest income	47	27	126	91
Total	35,687	40,506	58,263	36,926
Income Before Income Taxes	34,436	39,434	54,243	30,369
Income tax expense	(1,139)	(1,170)	(3,584)	(4,406)
Net Income	35,575	40,604	57,827	34,775
Comprehensive Income (Loss)	42,610	37,520	56,435	41,113
Subsidiary Issuer / Guarantor
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Number of pass-through trusts	2		2
Noncontrolling Interest, Ownership Percentage by Parent	100.00%		100.00%
Operating Revenue	638,414	599,361	1,737,520	1,623,602
Operating Expenses:
Aircraft fuel, including taxes and delivery	182,219	181,334	527,497	525,046
Wages and benefits	114,469	112,150	334,441	318,269
Aircraft rent	26,724	27,575	79,098	81,879
Maintenance materials and repairs	51,029	51,705	167,499	160,000
Aircraft and passenger servicing	31,848	31,080	92,929	89,367
Commissions and other selling	32,024	32,302	94,149	98,333
Depreciation and amortization	23,654	22,092	69,496	60,993
Other rentals and landing fees	23,632	21,996	65,850	60,773
Other	45,291	43,530	134,729	122,837
Total	530,890	523,764	1,565,688	1,517,497
Operating Income	107,524	75,597	171,832	106,105
Nonoperating Income (Expense):
Interest expense and amortization of debt discounts and issuance costs	(14,844)	(11,272)	(41,461)	(30,544)
Interest income	424	146	962	335
Capitalized interest	1,834	3,005	6,584	9,336
Gains (losses) on fuel derivatives	(27,892)	2,536	(28,506)	(10,931)
Other, net	(5,114)	749	(3,804)	(3,457)
Total	(45,592)	(4,836)	(66,225)	(35,261)
Income Before Income Taxes	61,932	70,761	105,607	70,844
Income tax expense	23,928	27,984	40,808	27,885
Net Income	38,004	42,777	64,799	42,959
Comprehensive Income (Loss)	45,039	39,693	63,407	49,297
Non-Guarantor Subsidiaries
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	1,145	(3)	2,801	634
Operating Expenses:
Maintenance materials and repairs	264		503
Commissions and other selling	11		43
Depreciation and amortization	730		1,464
Other	244	88	803	283
Total	1,249	88	2,813	283
Operating Income	(104)	(91)	(12)	351
Nonoperating Income (Expense):
Income Before Income Taxes	(104)	(91)	(12)	351
Net Income	(104)	(91)	(12)	351
Comprehensive Income (Loss)	(104)	(91)	(12)	351
Eliminations
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	(97)	(60)	(281)	(256)
Operating Expenses:
Commissions and other selling	(20)	(14)	(69)	(48)
Other	(77)	(46)	(212)	(208)
Total	(97)	(60)	(281)	(256)
Nonoperating Income (Expense):
Undistributed net income of subsidiaries	(37,900)	(42,686)	(64,787)	(43,310)
Total	(37,900)	(42,686)	(64,787)	(43,310)
Income Before Income Taxes	(37,900)	(42,686)	(64,787)	(43,310)
Net Income	(37,900)	(42,686)	(64,787)	(43,310)
Comprehensive Income (Loss)	$ (44,935)	$ (39,602)	$ (63,395)	$ (49,648)