Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
9 Months Ended
Sep. 30, 2018
Nov. 01, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Trading Symbol MMI  
Entity Registrant Name Marcus & Millichap, Inc.  
Entity Central Index Key 0001578732  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Smaller Reporting Company false  
Emerging Growth Company true  
Entity Extended Transition Period true  
Entity Common Stock, Shares Outstanding   38,651,360