Marcus & Millichap, Inc. Quarterly report pursuant to Section 13 or 15(d)

Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Other Assets [Line Items]
Allowance of doubtful accounts	$ 404		$ 404		$ 514
Provision of bad debt expense	88	$ 81	75	$ 52
Write-off receivables	$ 82	$ 17	185	72
Reduction of accrued bonuses and other employee related expenses in settlement of employee notes receivable			$ 60	$ 192
Minimum [Member]
Other Assets [Line Items]
Notes receivable due period			1 year
Maximum [Member]
Other Assets [Line Items]
Notes receivable due period			5 years