XML 72 R57.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Stock-Based Compensation Plans - Changes in Company's Common Stock Price During Reporting Period (Detail) - Stock Based Compensation Expense [Member] - $ / shares | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2016 | Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Common stock price at beginning of period | $ 25.41 | $ 46.14 | $ 29.14 | $ 33.25
Common stock price at end of period | 26.15 | 45.99 | 26.15 | 45.99
Increase (decrease) in stock price | $ 0.74 | $ (0.15) | $ (2.99) | $ 12.74

X
- Definition Increase decrease in common stock price. + References No definition available. + Details
Name: | mmi_IncreaseDecreaseInCommonStockPrice
Namespace Prefix: | mmi_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Price of a single share of a number of saleable stocks of a company. + References No definition available. + Details
Name: | us-gaap_SharePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_AwardTypeAxis=mmi_StockBasedCompensationExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |