Summary of Significant Accounting Policies - Cash Proceeds Received from the Sale of Mileage Credits (Details) (Marketing Component, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Marketing Component
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cash proceeds from sale of miles to non-airline third parties	$ 24,938	$ 20,954	$ 20,748
Portion of proceeds recognized immediately as marketing component	$ 20,998	$ 16,580	$ 10,576