Quarterly report pursuant to Section 13 or 15(d)

Related-Party Transactions - Additional Information (Detail)

v3.20.2
Related-Party Transactions - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Related Party Transaction [Line Items]          
Operating lease cost $ 6,355,000 $ 6,148,000 $ 18,959,000 $ 18,163,000  
Aggregate principal amount for employee notes receivable 498,000   498,000   $ 388,000
MMC [Member]          
Related Party Transaction [Line Items]          
Real estate brokerage commissions and financing fees from transactions with subsidiaries of Marcus & Millichap Company 225,000 1,200,000 1,900,000 4,000,000.0  
Commission expenses for transactions with subsidiaries of Marcus & Millichap Company 130,000 688,000 1,100,000 2,300,000  
Operating lease cost 333,000 333,000 998,000 999,000  
Accounts payable and other liabilities - related party 89,000   89,000   $ 88,000
MMC [Member] | Transition Services Agreement [Member]          
Related Party Transaction [Line Items]          
Selling, general and administrative expense $ 10,000 $ 21,000 $ 52,000 $ 96,000  
George M. Marcus [Member]          
Related Party Transaction [Line Items]          
Beneficial ownership percentage     40.00%