Document And Entity Information - shares
6 Months Ended
Jun. 30, 2019
Jul. 15, 2019
Document and Entity Information [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
Document Transition Report false  
Entity File Number 001-33166  
Entity Registrant Name Allegiant Travel Co  
Entity Incorporation, State or Country Code NV  
Entity Tax Identification Number 20-4745737  
Entity Address, Address Line One 1201 North Town Center Drive  
Entity Address, City or Town Las Vegas,  
Entity Address, State or Province NV  
Entity Address, Postal Zip Code 89144  
City Area Code 702  
Local Phone Number 851-7300  
Title of 12(b) Security Common stock, par value $.001  
Trading Symbol ALGT  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Shell Company true  
Entity Common Stock, Shares Outstanding   16,306,083
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Entity Central Index Key 0001362468  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2