Summary of Financial Statement Preparation and Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Minimum [Member] Support equipment [Member]	Dec. 31, 2012 Minimum [Member] Vehicles and other equipment [Member]	Dec. 31, 2012 Maximum [Member] Support equipment [Member]	Dec. 31, 2012 Maximum [Member] Vehicles and other equipment [Member]	Dec. 31, 2012 DC-8 combi aircraft and flight equipment [Member] Aircraft and Flight Equipment [Member]	Dec. 31, 2012 Boeing 767 and 757 aircraft and flight equipment [Member] Minimum [Member] Aircraft and Flight Equipment [Member]	Dec. 31, 2012 Boeing 767 and 757 aircraft and flight equipment [Member] Maximum [Member] Aircraft and Flight Equipment [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life				5 years	3 years	10 years	8 years	1 year	10 years	20 years
Capitalized interest	$ 2.8	$ 2.2	$ 1.5
Other liabilities for self-insured reserves	$ 31.6	$ 31.2