Condensed Consolidating Financial Information (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 328,255	$ 423,384	$ 441,398	$ 405,880
Restricted cash	6,566	19,434
Short-term investments	253,300	0
Accounts receivable, net	82,902	74,245
Spare parts and supplies, net	20,287	19,767
Deferred tax assets, net	17,325	17,325
Prepaid expenses and other	47,677	51,652
Total	756,312	605,807
Property and equipment at cost	1,975,705	1,661,434
Less accumulated depreciation and amortization	(344,727)	(327,102)
Property and equipment, net	1,630,978	1,334,332
Long-term prepayments and other	99,323	91,953
Restricted cash	0	1,566
Goodwill and other intangible assets, net	128,623	130,603
Total Assets	2,615,236	2,164,261
Current liabilities:
Accounts payable	78,350	89,787
Air traffic liability	487,525	409,086
Other accrued liabilities	114,717	97,571
Current maturities of long-term debt, less discount, and capital lease obligations	171,054	62,187
Total	851,646	658,631
Long-term debt and capital lease obligations	885,486	744,286
Other liabilities and deferred credits:
Accumulated pension and other postretirement benefit obligations	268,703	264,106
Other liabilities and deferred credits	70,129	59,424
Deferred tax liabilities, net	78,513	40,950
Total	417,345	364,480
Shareholders’ equity	460,759	396,864
Total Liabilities and Shareholders’ Equity	2,615,236	2,164,261
Parent Issuer / Guarantor
Current assets:
Cash and cash equivalents	48,982	84,797	84,311	83,626
Accounts receivable, net	236	1,192
Prepaid expenses and other	3
Total	49,221	85,989
Long-term prepayments and other	777	1,171
Deferred tax assets, net	18,462	14,767
Intercompany receivable	58,518	25,286
Investment in consolidated subsidiaries	414,702	348,040
Total Assets	541,680	475,253
Current liabilities:
Accounts payable	596	532
Other accrued liabilities	420	1,307
Current maturities of long-term debt, less discount, and capital lease obligations	79,579
Total	80,595	1,839
Long-term debt and capital lease obligations		76,550
Other liabilities and deferred credits:
Other liabilities and deferred credits	326
Total	326
Shareholders’ equity	460,759	396,864
Total Liabilities and Shareholders’ Equity	541,680	475,253
Subsidiary Issuer / Guarantor
Current assets:
Cash and cash equivalents	275,773	333,663	352,115	303,967
Restricted cash	6,566	19,434
Short-term investments	253,300
Accounts receivable, net	82,743	73,241
Spare parts and supplies, net	19,359	19,767
Deferred tax assets, net	17,325	17,325
Prepaid expenses and other	47,557	51,613
Total	702,623	515,043
Property and equipment at cost	1,941,036	1,629,517
Less accumulated depreciation and amortization	(343,263)	(327,102)
Property and equipment, net	1,597,773	1,302,415
Long-term prepayments and other	98,546	90,782
Restricted cash		1,566
Goodwill and other intangible assets, net	128,623	130,603
Total Assets	2,527,565	2,040,409
Current liabilities:
Accounts payable	77,565	88,990
Air traffic liability	485,624	407,359
Other accrued liabilities	114,152	96,264
Current maturities of long-term debt, less discount, and capital lease obligations	91,475	62,187
Total	768,816	654,800
Long-term debt and capital lease obligations	885,486	667,736
Intercompany payable	58,518	25,286
Other liabilities and deferred credits:
Accumulated pension and other postretirement benefit obligations	268,703	264,106
Other liabilities and deferred credits	69,053	59,424
Deferred tax liabilities, net	96,975	55,717
Total	434,731	379,247
Shareholders’ equity	380,014	313,340
Total Liabilities and Shareholders’ Equity	2,527,565	2,040,409
Non-Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	3,500	4,924	4,972	18,287
Accounts receivable, net	51	31
Spare parts and supplies, net	928
Prepaid expenses and other	117	39
Total	4,596	4,994
Property and equipment at cost	34,669	31,917
Less accumulated depreciation and amortization	(1,464)
Property and equipment, net	33,205	31,917
Total Assets	37,801	36,911
Current liabilities:
Accounts payable	317	484
Air traffic liability	1,901	1,727
Other accrued liabilities	145
Total	2,363	2,211
Other liabilities and deferred credits:
Other liabilities and deferred credits	750
Total	750
Shareholders’ equity	34,688	34,700
Total Liabilities and Shareholders’ Equity	37,801	36,911
Eliminations
Current assets:
Accounts receivable, net	(128)	(219)
Total	(128)	(219)
Deferred tax assets, net	(18,462)	(14,767)
Intercompany receivable	(58,518)	(25,286)
Investment in consolidated subsidiaries	(414,702)	(348,040)
Total Assets	(491,810)	(388,312)
Current liabilities:
Accounts payable	(128)	(219)
Total	(128)	(219)
Intercompany payable	(58,518)	(25,286)
Other liabilities and deferred credits:
Deferred tax liabilities, net	(18,462)	(14,767)
Total	(18,462)	(14,767)
Shareholders’ equity	(414,702)	(348,040)
Total Liabilities and Shareholders’ Equity	$ (491,810)	$ (388,312)