Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans - Subsequent to the IPO - 2013 Omnibus Equity Incentive Plan - Additional Information (Detail)

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Stock-Based Compensation Plans - Subsequent to the IPO - 2013 Omnibus Equity Incentive Plan - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended 12 Months Ended 0 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2013
Dec. 31, 2013
2013 Omnibus Equity Incentive Plan [Member]
Incentive_Plan
Dec. 31, 2013
Non-employee directors [Member]
Dec. 31, 2013
Non-Employee Director [Member]
Dec. 31, 2013
Employee [Member]
Dec. 31, 2013
Independent Contractors [Member]
Dec. 31, 2013
Deferred stock units [Member]
MMREIS managing directors [Member]
2013 Omnibus Equity Incentive Plan [Member]
Dec. 31, 2013
Deferred stock units [Member]
Millichap [Member]
2013 Omnibus Equity Incentive Plan [Member]
Dec. 31, 2013
Restricted Stock [Member]
Dec. 31, 2012
Restricted Stock [Member]
Dec. 31, 2011
Restricted Stock [Member]
Dec. 31, 2013
Restricted Stock [Member]
Non-employee directors [Member]
Dec. 31, 2013
Restricted Stock [Member]
Non-employee directors [Member]
2013 Omnibus Equity Incentive Plan [Member]
Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
Minimum [Member]
Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
Maximum [Member]
Nov. 30, 2013
Restricted Stock Units (RSUs) [Member]
2013 Omnibus Equity Incentive Plan [Member]
Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
Employee [Member]
Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
Independent Contractors [Member]
Dec. 31, 2013
Options & SARs [Member]
Minimum [Member]
Dec. 31, 2013
Options & SARs [Member]
Maximum [Member]
Dec. 31, 2013
Performance Shares [Member]
Dec. 31, 2013
Performance Shares [Member]
Minimum [Member]
Dec. 31, 2013
Performance Shares [Member]
Maximum [Member]
Dec. 31, 2013
Options [Member]
Dec. 31, 2013
SARs [Member]
Dec. 31, 2012
SARs [Member]
Dec. 31, 2011
SARs [Member]
Dec. 31, 2013
Restricted Stock Units and Awards [Member]
Non-employee directors [Member]
2013 Omnibus Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                        
Number of active equity plans   1                                                    
Common stock shares reserved for issuance of awards   5,500,000                                                    
Common stock shares available for grant   2,310,338                                                    
Common stock available for future issuance authorized annual percentage increase   3.00%                                                    
Fully vested deferred stock units 2,200,000           2,192,413 83,334                                        
Share-based award granted in connection with IPO 913,915               750 3,500 6,462 30,000 30,000     883,915 313,155 570,760               750 6,937  
Description of awards granted under the 2013 Plan   In connection with the IPO, MMI issued the following equity awards under the 2013 Plan: (i) DSUs for an aggregate of 2,192,413 shares granted as replacement awards to the MMREIS managing directors, (ii) DSUs for 83,334 shares to be granted to the Company’s Co-chairman of board of directors (Mr. Millichap) and (iii) 30,000 shares of restricted stock to the Company’s non-employee directors, in each case, based on the IPO price of $12.00.                                                    
Initial offering price per share   $ 12.00                                                    
Share-based payment award vesting rights, percentage     33.33%                         20.00%                        
Restricted stock units legal vesting date                               Jan. 02, 2015                        
Share limitations to awards granted under the 2013 Plan                           500,000 1,000,000       500,000 1,000,000   500,000 1,000,000          
Grant date fair value limitations to awards granted under the 2013 Plan                                           $ 2 $ 5          
Issued and outstanding options, SARs and performance awards under the 2013 Plan                                         0     0 0      
Non vested and expected to vest RSUs value 0.9                                                      
Non vested and expected to vest RSU intrinsic value 13.6     0.4 4.7 8.5                                            
Period for nonvested restricted stock units                                                       4 years 9 months 11 days
Unrecognized stock-based compensation expense $ 12.2   $ 0.3   $ 4.2 $ 7.7                                            
Period for unrecognized compensation expense is expected to recognized                                                       4 years 9 months 11 days