v3.25.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2025
Apr. 23, 2025
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Entity Registrant Name Saia, Inc.  
Entity Central Index Key 0001177702  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   26,634,005
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Shell Company false  
Entity File Number 0-49983  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 48-1229851  
Document Quarterly Report true  
Document Transition Report false  
Entity Address, Address Line One 11465 Johns Creek Parkway  
Entity Address, Address Line Two Suite 400  
Entity Address, City or Town Johns Creek  
Entity Address, State or Province GA  
Entity Address, Postal Zip Code 30097  
City Area Code 770  
Local Phone Number 232-5067  
Title of each class Common Stock, par value $.001 per share  
Trading Symbol SAIA  
Security Exchange Name NASDAQ