Marcus & Millichap, Inc. Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans - Amendments to Restricted Stock and SARs - Additional Information (Detail) - shares		12 Months Ended
	Oct. 30, 2013	Dec. 31, 2017
Deferred stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee termination age	67 years
DSU settlement to common stock percentage	20.00%
DSU settlement into actual stock issued term	5 years
Percentage of shares of deferred stock units settled in the event of death or termination after reaching age 67	100.00%
Restricted Stock Sales Restriction [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sales restriction lapse percentage for restricted stock	20.00%
Employee termination age	67 years
Sales restriction period for restricted stock	5 years
Percentage of shares of stock released from resale restriction upon consummation of change of control	100.00%
Percentage of shares of restricted released from resale restriction in the event of death or termination after reaching age 67	100.00%
Number of original shares subject to resale restriction	3,689,326
Number of shares remain subject to sales restriction		732,020