Condensed Consolidating Financial Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Condensed Consolidating Statements of Operations and Comprehensive Income
Operating Revenue	$ 575,720	$ 533,928	$ 1,100,578	$ 1,024,682
Operating Expenses:
Aircraft fuel, including taxes and delivery	174,139	169,223	345,278	343,712
Wages and benefits	112,478	103,384	219,972	206,119
Aircraft rent	26,095	28,285	52,374	54,304
Maintenance materials and repairs	58,399	53,036	116,709	108,295
Aircraft and passenger servicing	30,860	29,228	61,081	58,287
Commissions and other selling	30,773	32,186	62,108	65,997
Depreciation and amortization	23,765	19,788	46,576	38,901
Other rentals and landing fees	21,656	19,630	42,218	38,777
Other	45,961	41,777	92,631	84,825
Total	524,126	496,537	1,038,947	999,217
Operating Income	51,594	37,391	61,631	25,465
Nonoperating Income (Expense):
Interest expense and amortization of debt discounts and issuance costs	(15,997)	(12,163)	(31,007)	(23,540)
Interest income	398	126	617	253
Capitalized interest	1,974	2,891	4,750	6,331
Gains (losses) on fuel derivatives	6,285	(6,906)	(614)	(13,467)
Other, net	725	(3,124)	1,310	(4,206)
Total	(6,615)	(19,176)	(24,944)	(34,629)
Income (Loss) Before Income Taxes	44,979	18,215	36,687	(9,164)
Income tax expense (benefit)	17,652	6,899	14,435	(3,335)
Net Income (Loss)	27,327	11,316	22,252	(5,829)
Comprehensive Income (Loss)	24,151	18,643	13,825	3,593
Parent Issuer / Guarantor
Operating Expenses:
Other	1,507	4,217	2,769	5,485
Total	1,507	4,217	2,769	5,485
Operating Income	(1,507)	(4,217)	(2,769)	(5,485)
Nonoperating Income (Expense):
Undistributed net income of subsidiaries	29,694	15,406	26,887	624
Interest expense and amortization of debt discounts and issuance costs	(2,210)	(2,158)	(4,390)	(4,268)
Interest income	40	28	79	64
Total	27,524	13,276	22,576	(3,580)
Income (Loss) Before Income Taxes	26,017	9,059	19,807	(9,065)
Income tax expense (benefit)	(1,310)	(2,257)	(2,445)	(3,236)
Net Income (Loss)	27,327	11,316	22,252	(5,829)
Comprehensive Income (Loss)	24,151	18,643	13,825	3,593
Subsidiary Issuer / Guarantor
Condensed Consolidating Statements of Operations and Comprehensive Income
Number of pass-through trusts	2		2
Ownership interest (as a percent)	100.00%		100.00%
Operating Revenue	574,779	533,993	1,099,106	1,024,241
Operating Expenses:
Aircraft fuel, including taxes and delivery	174,139	169,223	345,278	343,712
Wages and benefits	112,478	103,384	219,972	206,119
Aircraft rent	26,095	28,285	52,374	54,304
Maintenance materials and repairs	58,172	53,036	116,470	108,295
Aircraft and passenger servicing	30,860	29,228	61,081	58,287
Commissions and other selling	30,778	32,204	62,125	66,031
Depreciation and amortization	23,130	19,788	45,842	38,901
Other rentals and landing fees	21,656	19,630	42,218	38,777
Other	44,302	37,503	89,438	79,307
Total	521,610	492,281	1,034,798	993,733
Operating Income	53,169	41,712	64,308	30,508
Nonoperating Income (Expense):
Interest expense and amortization of debt discounts and issuance costs	(13,787)	(10,005)	(26,617)	(19,272)
Interest income	358	98	538	189
Capitalized interest	1,974	2,891	4,750	6,331
Gains (losses) on fuel derivatives	6,285	(6,906)	(614)	(13,467)
Other, net	725	(3,124)	1,310	(4,206)
Total	(4,445)	(17,046)	(20,633)	(30,425)
Income (Loss) Before Income Taxes	48,724	24,666	43,675	83
Income tax expense (benefit)	18,962	9,156	16,880	(99)
Net Income (Loss)	29,762	15,510	26,795	182
Comprehensive Income (Loss)	26,586	22,837	18,368	9,604
Non-Guarantor Subsidiaries
Condensed Consolidating Statements of Operations and Comprehensive Income
Operating Revenue	1,025	22	1,656	637
Operating Expenses:
Maintenance materials and repairs	227		239
Commissions and other selling	19		32
Depreciation and amortization	635		734
Other	212	126	559	195
Total	1,093	126	1,564	195
Operating Income	(68)	(104)	92	442
Nonoperating Income (Expense):
Income (Loss) Before Income Taxes	(68)	(104)	92	442
Net Income (Loss)	(68)	(104)	92	442
Comprehensive Income (Loss)	(68)	(104)	92	442
Eliminations
Condensed Consolidating Statements of Operations and Comprehensive Income
Operating Revenue	(84)	(87)	(184)	(196)
Operating Expenses:
Commissions and other selling	(24)	(18)	(49)	(34)
Other	(60)	(69)	(135)	(162)
Total	(84)	(87)	(184)	(196)
Nonoperating Income (Expense):
Undistributed net income of subsidiaries	(29,694)	(15,406)	(26,887)	(624)
Total	(29,694)	(15,406)	(26,887)	(624)
Income (Loss) Before Income Taxes	(29,694)	(15,406)	(26,887)	(624)
Net Income (Loss)	(29,694)	(15,406)	(26,887)	(624)
Comprehensive Income (Loss)	$ (26,518)	$ (22,733)	$ (18,460)	$ (10,046)