Summary of Significant Accounting Policies - Primary Components of Non-Ticket Revenue (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Product Information [Line Items]
Non-ticket revenue	$ 786,608	$ 668,367	$ 535,596
Baggage
Product Information [Line Items]
Non-ticket revenue	318,103	275,958	217,536
Passenger usage fee
Product Information [Line Items]
Non-ticket revenue	221,992	188,911	149,577
Advance seat selection
Product Information [Line Items]
Non-ticket revenue	76,270	59,241	48,956
Service charges for changes and cancellations
Product Information [Line Items]
Non-ticket revenue	38,388	32,546	27,762
Other
Product Information [Line Items]
Non-ticket revenue	$ 131,855	$ 111,711	$ 91,765