Commitments and Contingencies - Employees (Details) (USD $) In Millions, unless otherwise specified				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Number of employees, total Unionized employees concentration risk	Dec. 31, 2011 Number of employees, total Unionized employees concentration risk	Dec. 31, 2012 Number of employees, total Unionized employees concentration risk Air Line Pilots Association, International	Dec. 31, 2012 Number of employees, total Unionized employees concentration risk Association of Flight Attendants	Dec. 31, 2012 Number of employees, total Unionized employees concentration risk Transport Workers Union
Concentration Risk [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)				54.00%	52.00%	22.00%	31.00%	1.00%
Accrued Health Care Claims	$ 1.9	$ 2.0	$ 2.1