Condensed Consolidating Financial Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	$ 599,298	$ 549,322	$ 1,623,980	$ 1,469,367
Operating Expenses:
Aircraft fuel, including taxes and delivery	181,334	165,762	525,046	456,545
Wages and benefits	112,150	93,438	318,269	280,261
Aircraft rent	27,575	25,626	81,879	73,712
Maintenance materials and repairs	51,705	44,150	160,000	137,271
Aircraft and passenger servicing	31,080	28,859	89,367	74,859
Commissions and other selling	32,288	31,028	98,285	89,055
Depreciation and amortization	22,092	22,983	60,993	63,687
Other rentals and landing fees	21,996	22,520	60,773	63,486
Other	44,644	40,023	129,469	113,330
Total	524,864	474,389	1,524,081	1,352,206
Operating Income	74,434	74,933	99,899	117,161
Nonoperating Income (Expense):
Interest expense and amortization of debt discounts and issuance costs	(13,479)	(11,975)	(37,019)	(31,745)
Interest income	173	96	426	477
Capitalized interest	3,005	2,579	9,336	7,328
Gains (losses) on fuel derivatives	2,536	6,508	(10,931)	(2,495)
Other, net	749	1,662	(3,457)	1,245
Total	(7,016)	(1,130)	(41,645)	(25,190)
Income Before Income Taxes	67,418	73,803	58,254	91,971
Income tax expense (benefit)	26,814	28,320	23,479	35,326
Net Income	40,604	45,483	34,775	56,645
Total Comprehensive Income, net	37,520	47,346	41,113	60,765
Parent Issuer / Guarantor
Operating Expenses:
Other	1,072	1,484	6,557	3,882
Total	1,072	1,484	6,557	3,882
Operating Income	(1,072)	(1,484)	(6,557)	(3,882)
Nonoperating Income (Expense):
Undistributed net income of subsidiaries	42,686	47,791	43,310	63,120
Interest expense and amortization of debt discounts and issuance costs	(2,207)	(2,105)	(6,475)	(6,201)
Interest income	27	30	91	88
Total	40,506	45,716	36,926	57,007
Income Before Income Taxes	39,434	44,232	30,369	53,125
Income tax expense (benefit)	(1,170)	(1,251)	(4,406)	(3,520)
Net Income	40,604	45,483	34,775	56,645
Total Comprehensive Income, net	37,520	47,346	41,113	60,765
Subsidiary Issuer / Guarantor
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Number of pass-through trusts	2		2
Ownership interest (as a percent)	100.00%		100.00%
Operating Revenue	599,361	549,365	1,623,602	1,469,539
Operating Expenses:
Aircraft fuel, including taxes and delivery	181,334	165,762	525,046	456,545
Wages and benefits	112,150	93,438	318,269	280,261
Aircraft rent	27,575	25,626	81,879	73,712
Maintenance materials and repairs	51,705	44,150	160,000	137,271
Aircraft and passenger servicing	31,080	28,859	89,367	74,859
Commissions and other selling	32,302	31,037	98,333	89,088
Depreciation and amortization	22,092	22,983	60,993	63,687
Other rentals and landing fees	21,996	22,520	60,773	63,486
Other	43,530	38,560	122,837	109,526
Total	523,764	472,935	1,517,497	1,348,435
Operating Income	75,597	76,430	106,105	121,104
Nonoperating Income (Expense):
Interest expense and amortization of debt discounts and issuance costs	(11,272)	(9,870)	(30,544)	(25,544)
Interest income	146	66	335	389
Capitalized interest	3,005	2,579	9,336	7,328
Gains (losses) on fuel derivatives	2,536	6,508	(10,931)	(2,495)
Other, net	749	1,662	(3,457)	1,245
Total	(4,836)	945	(35,261)	(19,077)
Income Before Income Taxes	70,761	77,375	70,844	102,027
Income tax expense (benefit)	27,984	29,571	27,885	38,846
Net Income	42,777	47,804	42,959	63,181
Total Comprehensive Income, net	39,693	49,667	49,297	67,301
Non-Guarantor Subsidiaries
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	(3)	9	634	32
Operating Expenses:
Other	88	22	283	93
Total	88	22	283	93
Operating Income	(91)	(13)	351	(61)
Nonoperating Income (Expense):
Income Before Income Taxes	(91)	(13)	351	(61)
Net Income	(91)	(13)	351	(61)
Total Comprehensive Income, net	(91)	(13)	351	(61)
Eliminations
Condensed Consolidating Statements of Operations and Comprehensive Income (Loss)
Operating Revenue	(60)	(52)	(256)	(204)
Operating Expenses:
Commissions and other selling	(14)	(9)	(48)	(33)
Other	(46)	(43)	(208)	(171)
Total	(60)	(52)	(256)	(204)
Nonoperating Income (Expense):
Undistributed net income of subsidiaries	(42,686)	(47,791)	(43,310)	(63,120)
Total	(42,686)	(47,791)	(43,310)	(63,120)
Income Before Income Taxes	(42,686)	(47,791)	(43,310)	(63,120)
Net Income	(42,686)	(47,791)	(43,310)	(63,120)
Total Comprehensive Income, net	$ (39,602)	$ (49,654)	$ (49,648)	$ (67,240)