Summary of Significant Accounting Policies - Primary Components of Non-Ticket Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Product Information [Line Items]
Non-ticket revenue	$ 1,121,335	$ 972,125	$ 786,608
Baggage
Product Information [Line Items]
Non-ticket revenue	434,269	381,386	318,103
Passenger usage fee
Product Information [Line Items]
Non-ticket revenue	358,920	298,092	221,992
Advance seat selection
Product Information [Line Items]
Non-ticket revenue	110,966	97,786	76,270
Service charges for changes and cancellations
Product Information [Line Items]
Non-ticket revenue	42,823	43,756	38,388
Other
Product Information [Line Items]
Non-ticket revenue	$ 174,357	$ 151,105	$ 131,855