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

Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 24,976	$ 14,712
Fair Value	25,331	14,752
Long-term marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	24,976	14,712
Gross Unrealized Gains	367	59
Gross Unrealized Losses	(12)	(19)
Fair Value	25,331	14,752
Long-term marketable securities [Member] \| U.S. government and agency debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,037	4,993
Gross Unrealized Gains	63	7
Gross Unrealized Losses	(7)	(3)
Fair Value	7,093	4,997
Long-term marketable securities [Member] \| Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,940	7,442
Gross Unrealized Gains	252	48
Gross Unrealized Losses	(5)	(12)
Fair Value	14,187	7,478
Long-term marketable securities [Member] \| Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,999	2,277
Gross Unrealized Gains	52	4
Gross Unrealized Losses		(4)
Fair Value	$ 4,051	$ 2,277