XML 10 R1.htm IDEA: XBRL DOCUMENT v3.25.3
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2025
Oct. 31, 2025
Document And Entity Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q3  
Entity Registrant Name CarGurus, Inc.  
Trading Symbol CARG  
Entity Central Index Key 0001494259  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Current Reporting Status Yes  
Entity File Number 001-38233  
Entity Tax Identification Number 04-3843478  
Entity Address, Address Line One 1001 Boylston Street  
Entity Address, Address Line Two 16th Floor  
Entity Address, City or Town Boston  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02115  
City Area Code 617  
Local Phone Number 354-0068  
Entity Interactive Data Current Yes  
Document Quarterly Report true  
Document Transition Report false  
Entity Incorporation, State or Country Code DE  
Title of 12(b) Security Class A Common Stock, par value $0.001 per share  
Security Exchange Name NASDAQ  
Class A Common Stock    
Document And Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   81,236,954
Class B Common Stock    
Document And Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   14,216,250