Advances and loans and commissions receivable allowance for credit loss.

No definition available.

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Balance Type:	credit
Period Type:	instant

- Definition

Maximum payment deferral period for certain commissions payable.

+ References

No definition available.

+ Details

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- Definition

Deferred Compensation Liability, Payout Period

+ References

No definition available.

+ Details

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- Definition

The amount the Company may, in its sole and absolute discretion, elect to withdraw at any time all or a portion of the amount by which the fair market value of the Deferred Compensation Plan's assets exceeds the stated percentage of the aggregate amount credited to the Deferred Compensation Plan's participants' accounts.

+ References

No definition available.

+ Details

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- Definition

Number Of Annual Installments

+ References

No definition available.

+ Details

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- Definition

Payments for deferred compensation and commissions.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Payments (consisting of principal or interest or principal and interest) for stock appreciation rights liability.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Schedule Of Accrued Expenses [Line Items]

+ References

No definition available.

+ Details

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- Definition

Interest accrual rate for the outstanding balance on the SARs liability.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Stock Appreciation Rights Liability Noncurrent

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No definition available.

+ Details

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Namespace Prefix:	mmi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Treasury note term rate used to determine SARs liability interest accrual rate.

+ References

No definition available.

+ Details

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Namespace Prefix:	mmi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of interest expense classified as nonoperating.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

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Data Type:	xbrli:monetaryItemType
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- Details

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- Details

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Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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Selected Balance Sheet Data - Narrative (Details) $ in Thousands				3 Months Ended		6 Months Ended
	Jan. 01, 2026	Jan. 01, 2025	Jan. 01, 2014	Jun. 30, 2026 USD ($) installment	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($) installment	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)	Mar. 31, 2013 USD ($)
Schedule Of Accrued Expenses [Line Items]
Advances and loans and commissions receivable allowance for credit loss				$ 1,100		$ 1,100		$ 1,100
SARs frozen liability amount				6,707		6,707		$ 7,343
Interest expense				$ 140	$ 200	$ 293	$ 387
Commissions Payable
Schedule Of Accrued Expenses [Line Items]
Maximum payment deferral period for certain commissions payable						3 years
SARs
Schedule Of Accrued Expenses [Line Items]
SARs frozen liability amount									$ 20,000
Number of annual installments \| installment				10		10
Treasury note term			10 years
Base spread on SARs liability variable rate			2.00%
SARs liability interest accrual rates	6.19%	6.57%
Interest expense				$ 113	157	$ 227	313
Payments for SARs Liability				$ 2,800	$ 2,600	$ 2,800	2,600
Deferred Compensation Liability
Schedule Of Accrued Expenses [Line Items]
Fair value of deferred compensation plan assets						110.00%
Payments made during the period						$ 162	$ 230
Deferred Compensation Liability \| Minimum
Schedule Of Accrued Expenses [Line Items]
Payout period						2 years
Deferred Compensation Liability \| Maximum
Schedule Of Accrued Expenses [Line Items]
Payout period						15 years