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

Earnings per Share - Computation of Basic and Diluted Earnings Per Share, Including Antidilutive Securities Excluded from Computation of Earnings Per Share (Parenthetical) (Detail) - Restricted Stock Awards [Member] - 2013 Omnibus Equity Incentive Plan [Member]	12 Months Ended
	Dec. 31, 2019
Minimum [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Vesting period	1 year
Maximum [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Vesting period	3 years