Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans - Pre-IPO - Additional Information (Detail)

v2.4.1.9
Stock-Based Compensation Plans - Pre-IPO - Additional Information (Detail)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized stock-based compensation expenses recognition period 4 years 1 month 24 days    
Notes receivable from employees [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Notes issued, interest rate 5.00%mmi_NotesReceivableItInterestRateStatedPercentageRateRangeMinimum
/ us-gaap_LongtermDebtTypeAxis
= mmi_NotesReceivableFromEmployeesMember
   
Notes issued, interest rate 6.00%mmi_NotesReceivableItInterestRateStatedPercentageRateRangeMaximum
/ us-gaap_LongtermDebtTypeAxis
= mmi_NotesReceivableFromEmployeesMember
   
Notes issued, payment date Apr. 15, 2016    
Pre-IPO [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of stock option redemption or cancelations   0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_StatementScenarioAxis
= mmi_PreIpoMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_StatementScenarioAxis
= mmi_PreIpoMember
Unrecognized stock-based compensation expenses recognition period 4 years    
Pre-IPO [Member] | Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted common stock issued, vesting period 3 years    
Pre-IPO [Member] | Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted common stock issued, vesting period 5 years    
Restricted Common Stock [Member] | Pre-IPO [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Terms of Issued Options One year or less