Property and Equipment (Schedule of Property and Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,272,206	$ 1,203,401
Accumulated depreciation	(416,252)	(384,477)
Property and equipment, net	855,954	818,924
Aircraft and flight equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,217,891	1,148,781
Support equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	51,680	52,209
Vehicles and other equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,653	1,597
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 982	$ 814

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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