Summary of Significant Accounting Policies - Frequent Flier Program (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012 Transportation Component
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Affinity Card Program, deferred fair value of the transportation component, recognition period			16 months
Liability for future FREE SPIRIT award redemptions and unrecognized revenue from the sale of mileage credits	$ 2.6	$ 2.4

Value of revenue deferred or cost to provide future products or services, primarily air transportation, associated with programs used by airlines to encourage passenger loyalty by providing rewards geared to the frequency of travel on the sponsoring airline, typically in the form of frequent flyer miles, points, or segments that can be accumulated and converted into free or discounted travel or other redemption options. Used to reflect the current portion of the liability (within one year or within the normal operating cycle if longer).

No definition available.

Name:	us-gaap_FrequentFlierLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant