Annual report pursuant to Section 13 and 15(d)

Accounting Policies - Additional Information (Detail)

v2.4.1.9
Accounting Policies - Additional Information (Detail) (USD $)
 12 Months Ended 0 Months Ended 10 Months Ended
Dec. 31, 2014
Fund
Dec. 31, 2013
Dec. 31, 2012
Oct. 31, 2013
Oct. 31, 2013
Jun. 30, 2013
Financial_Institution
Accounting Policies [Line Items]            
Number of money market fund 1mmi_NumberOfMoneyMarketFund          
Description of cash sweep arrangement Historically, other than for a 2-week period around MMC's March 31 fiscal year end, the Company had a receivable from MMC for the cash that was swept. When the sweep arrangement was not in effect, during the week before and the week after March 31, the Company's cash balances remained in the Company's bank accounts.          
Sweep arrangement termination date Jun. 30, 2013          
Allowance for commissions receivable $ 0us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent $ 0us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent        
Capital lease obligations 0us-gaap_CapitalLeaseObligations          
Advertising expense 965,000us-gaap_AdvertisingExpense 975,000us-gaap_AdvertisingExpense 702,000us-gaap_AdvertisingExpense      
Income tax benefit realized, percentage 50.00%mmi_IncomeTaxBenefitRecognitionCriteriaPercentageThreshold          
Uncertain tax positions $ 0us-gaap_LiabilityForUncertainTaxPositionsCurrent $ 0us-gaap_LiabilityForUncertainTaxPositionsCurrent        
Tax sharing agreement termination date Oct. 31, 2013          
Cash Operating Bank Account [Member]            
Accounting Policies [Line Items]            
Number of financial institutions           1mmi_NumberOfFinancialInstitutions
/ us-gaap_CashAndCashEquivalentsAxis
= mmi_CashOperatingBankAccountMember
Cash and Cash Equivalents Bank Accounts [Member]            
Accounting Policies [Line Items]            
Number of financial institutions 3mmi_NumberOfFinancialInstitutions
/ us-gaap_CashAndCashEquivalentsAxis
= mmi_CashAndCashEquivalentsBankAccountsMember 		3mmi_NumberOfFinancialInstitutions
/ us-gaap_CashAndCashEquivalentsAxis
= mmi_CashAndCashEquivalentsBankAccountsMember 		       
Employee Stock Purchase Plan [Member]            
Accounting Policies [Line Items]            
Length of purchase intervals 6 months          
Expected dividend yield 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= mmi_EmployeeStockPurchasePlanMember 		         
ESPP shares forfeiture rate 0.00%mmi_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate
/ us-gaap_AwardTypeAxis
= mmi_EmployeeStockPurchasePlanMember 		         
Tax-sharing agreement [Member]            
Accounting Policies [Line Items]            
Effective income tax rate, pre-IPO   43.50%us-gaap_EffectiveIncomeTaxRateContinuingOperations
/ us-gaap_TypeOfArrangementAxis
= mmi_TaxSharingAgreementMember 		43.50%us-gaap_EffectiveIncomeTaxRateContinuingOperations
/ us-gaap_TypeOfArrangementAxis
= mmi_TaxSharingAgreementMember 		43.50%us-gaap_EffectiveIncomeTaxRateContinuingOperations
/ us-gaap_TypeOfArrangementAxis
= mmi_TaxSharingAgreementMember 		   
Tax sharing agreement termination date Oct. 31, 2013          
Minimum [Member]            
Accounting Policies [Line Items]            
Property and equipment, estimated useful lives 3 years          
Minimum [Member] | Pre-IPO [Member]            
Accounting Policies [Line Items]            
Restricted common stock issued, vesting period         3 years  
Maximum [Member]            
Accounting Policies [Line Items]            
Commission's receivable settled period 10 days          
Property and equipment, estimated useful lives 7 years          
Maximum [Member] | Pre-IPO [Member]            
Accounting Policies [Line Items]            
Restricted common stock issued, vesting period         5 years