Condensed Consolidating Financial Information (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 360,281	$ 423,384	$ 477,588	$ 405,880
Restricted cash	20,379	19,434
Short-term investments	203,333
Accounts receivable, net	94,833	74,245
Spare parts and supplies, net	17,071	19,767
Deferred tax assets, net	17,325	17,325
Prepaid expenses and other	32,893	51,652
Total	746,115	605,807
Property and equipment at cost	1,970,905	1,661,434
Less accumulated depreciation and amortization	(346,750)	(327,102)
Property and equipment, net	1,624,155	1,334,332
Long-term prepayments and other	85,545	91,953
Restricted cash		1,566
Goodwill and other intangible assets, net	129,283	130,603
Total Assets	2,585,098	2,164,261
Current liabilities:
Accounts payable	87,886	89,787
Air traffic liability	537,088	409,086
Other accrued liabilities	94,650	97,571
Current maturities of long-term debt, less discount, and capital lease obligations	156,025	62,187
Total	875,649	658,631
Long-term debt and capital lease obligations	915,110	744,286
Other liabilities and deferred credits:
Accumulated pension and other postretirement benefit obligations	266,489	264,106
Other liabilities and deferred credits	60,375	59,424
Deferred tax liabilities, net	51,529	40,950
Total	378,393	364,480
Shareholders’ equity	415,946	396,864
Total Liabilities and Shareholders’ Equity	2,585,098	2,164,261
Parent Issuer / Guarantor
Current assets:
Cash and cash equivalents	45,764	84,797	85,200	83,626
Accounts receivable, net	1,096	1,192
Prepaid expenses and other	8
Total	46,868	85,989
Long-term prepayments and other	908	1,171
Deferred tax assets, net	17,213	14,767
Intercompany receivable	62,785	25,286
Investment in consolidated subsidiaries	368,818	348,040
Total Assets	496,592	475,253
Current liabilities:
Accounts payable	492	532
Other accrued liabilities	1,413	1,307
Current maturities of long-term debt, less discount, and capital lease obligations	78,538
Total	80,443	1,839
Long-term debt and capital lease obligations		76,550
Other liabilities and deferred credits:
Other liabilities and deferred credits	203
Total	203
Shareholders’ equity	415,946	396,864
Total Liabilities and Shareholders’ Equity	496,592	475,253
Subsidiary Issuer / Guarantor
Current assets:
Cash and cash equivalents	310,762	333,663	375,383	303,967
Restricted cash	20,379	19,434
Short-term investments	203,333
Accounts receivable, net	93,787	73,241
Spare parts and supplies, net	16,143	19,767
Deferred tax assets, net	17,325	17,325
Prepaid expenses and other	32,696	51,613
Total	694,425	515,043
Property and equipment at cost	1,937,148	1,629,517
Less accumulated depreciation and amortization	(346,016)	(327,102)
Property and equipment, net	1,591,132	1,302,415
Long-term prepayments and other	84,637	90,782
Restricted cash		1,566
Goodwill and other intangible assets, net	129,283	130,603
Total Assets	2,499,477	2,040,409
Current liabilities:
Accounts payable	87,223	88,990
Air traffic liability	535,101	407,359
Other accrued liabilities	93,092	96,264
Current maturities of long-term debt, less discount, and capital lease obligations	77,487	62,187
Total	792,903	654,800
Long-term debt and capital lease obligations	915,110	667,736
Intercompany payable	62,785	25,286
Other liabilities and deferred credits:
Accumulated pension and other postretirement benefit obligations	266,489	264,106
Other liabilities and deferred credits	59,422	59,424
Deferred tax liabilities, net	68,742	55,717
Total	394,653	379,247
Shareholders’ equity	334,026	313,340
Total Liabilities and Shareholders’ Equity	2,499,477	2,040,409
Non-Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	3,755	4,924	17,005	18,287
Accounts receivable, net	128	31
Spare parts and supplies, net	928
Prepaid expenses and other	189	39
Total	5,000	4,994
Property and equipment at cost	33,757	31,917
Less accumulated depreciation and amortization	(734)
Property and equipment, net	33,023	31,917
Total Assets	38,023	36,911
Current liabilities:
Accounts payable	349	484
Air traffic liability	1,987	1,727
Other accrued liabilities	145
Total	2,481	2,211
Other liabilities and deferred credits:
Other liabilities and deferred credits	750
Total	750
Shareholders’ equity	34,792	34,700
Total Liabilities and Shareholders’ Equity	38,023	36,911
Eliminations
Current assets:
Accounts receivable, net	(178)	(219)
Total	(178)	(219)
Deferred tax assets, net	(17,213)	(14,767)
Intercompany receivable	(62,785)	(25,286)
Investment in consolidated subsidiaries	(368,818)	(348,040)
Total Assets	(448,994)	(388,312)
Current liabilities:
Accounts payable	(178)	(219)
Total	(178)	(219)
Intercompany payable	(62,785)	(25,286)
Other liabilities and deferred credits:
Deferred tax liabilities, net	(17,213)	(14,767)
Total	(17,213)	(14,767)
Shareholders’ equity	(368,818)	(348,040)
Total Liabilities and Shareholders’ Equity	$ (448,994)	$ (388,312)