Annual report pursuant to Section 13 and 15(d)

Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail)

v2.4.1.9
Investments in Marketable Securities - Schedule of Amortized Cost and Fair Value of Marketable Securities, Available-for-Sale, by Type of Security (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost $ 14,712us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Fair Value 14,752us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
Long-term marketable securities [Member]  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost 14,712us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
Gross Unrealized Gains 59us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
Gross Unrealized Losses (19)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
Fair Value 14,752us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
Long-term marketable securities [Member] | U.S. government and agency debt securities [Member]  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost 4,993us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Gross Unrealized Gains 7us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Gross Unrealized Losses (3)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair Value 4,997us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Long-term marketable securities [Member] | Corporate debt securities [Member]  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost 7,442us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Gross Unrealized Gains 48us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Gross Unrealized Losses (12)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value 7,478us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Long-term marketable securities [Member] | Asset-backed securities [Member]  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost 2,277us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesMember
Gross Unrealized Gains 4us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesMember
Gross Unrealized Losses (4)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesMember
Fair Value $ 2,277us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
/ us-gaap_InvestmentTypeAxis
= mmi_LongTermInvestmentsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesMember