Summary of Financial Statement Preparation and Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Capitalized interest	$ 0.1	$ 1.1	$ 2.8
Other liabilities for self-insured reserves	$ 25.8	$ 28.3
Minimum [Member] | Ground equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Minimum [Member] | facilities, leasehold improvements and office equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Maximum [Member] | Ground equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Maximum [Member] | facilities, leasehold improvements and office equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	25 years
Boeing 767 and 757 aircraft and flight equipment [Member] | Minimum [Member] | Flight Equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Boeing 767 and 757 aircraft and flight equipment [Member] | Maximum [Member] | Flight Equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	18 years