Quarterly report pursuant to Section 13 or 15(d)

Description of Business, Basis of Presentation and Recent Accounting Pronouncements - Additional Information (Detail)

v2.4.1.9
Description of Business, Basis of Presentation and Recent Accounting Pronouncements - Additional Information (Detail)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Class of Stock [Line Items]    
Number of offices in the United States and Canada 78mmi_NumberOfOffices  
Contribution date Oct. 30, 2013  
Percentage of common stock distributed 80.00%mmi_PercentageOfCommonStockDistributed  
Maximum [Member]    
Class of Stock [Line Items]    
Commission's receivable settled period 10 days  
Customer Concentration Risk [Member] | Total revenues [Member] | Maximum [Member]    
Class of Stock [Line Items]    
Concentration of credit risk percentage 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Customer Concentration Risk [Member] | Commissions receivable [Member] | Maximum [Member]    
Class of Stock [Line Items]    
Concentration of credit risk percentage 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= mmi_CommissionReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= mmi_CommissionReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
MMI [Member]    
Class of Stock [Line Items]    
Formation date 2013-06