Segment Reporting - Additional Information (Detail)	6 Months Ended
Jun. 30, 2025 Segment
Segment Reporting Disclosure [Line Items]
Number of business segments	5
Number of operating segments	4
Number of non-operating segments	1
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember, srt:ChiefFinancialOfficerMember, srt:ChiefOperatingOfficerMember, srt:PresidentMember
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	The CODM primarily uses segment information to identify areas to improve efficiency of resources allocation, determine where to reinvest profits, and minimize unnecessary expenses. The CODM assesses segment performance mainly through selected financial ratios such as returns on average assets and net interest margin, which identifies areas requiring action.
Roofs [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	30.00%
Swimming Pools [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	30.00%
Windows [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	11.00%
Other Product Lines [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	10.00%
Texas [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	16.00%
Texas [Member] \| Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	12.00%
Florida [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	10.00%
Florida [Member] \| Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	13.00%
Other States [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	10.00%
Other States [Member] \| Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	10.00%
Geographic Concentration Risk [Member] \| Sales Revenue Net [Member] \| Recreational Vehicles [Member]
Segment Reporting Disclosure [Line Items]
Aggregate percentage of loans lending	54.00%
Geographic Concentration Risk [Member] \| Sales Revenue Net [Member] \| Boats [Member]
Segment Reporting Disclosure [Line Items]
Aggregate percentage of loans lending	21.00%
Geographic Concentration Risk [Member] \| Sales Revenue Net [Member] \| Cars [Member]
Segment Reporting Disclosure [Line Items]
Aggregate percentage of loans lending	12.00%
Geographic Concentration Risk [Member] \| Sales Revenue Net [Member] \| Other Product Lines [Member]
Segment Reporting Disclosure [Line Items]
Aggregate percentage of loans lending	10.00%
Commercial Lending Segment [Member] \| Manufacturing [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	57.00%
Commercial Lending Segment [Member] \| Construction [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	18.00%
Commercial Lending Segment [Member] \| Wholesale Trade [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	11.00%
Commercial Lending Segment [Member] \| Other Product Lines [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	10.00%
Commercial Lending Segment [Member] \| California [Member]
Segment Reporting Disclosure [Line Items]
Loan outstanding percent	29.00%
Commercial Lending Segment [Member] \| Geographic Concentration Risk [Member] \| Sales Revenue Net [Member] \| Other Product Lines [Member]
Segment Reporting Disclosure [Line Items]
Aggregate percentage of loans lending	10.00%

Number of non- operating segments.

No definition available.

Name:	mfin_NumberOfNonOperatingSegments
Namespace Prefix:	mfin_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Segment reporting disclosure.

+ References

No definition available.

+ Details

Name:	mfin_SegmentReportingDisclosureLineItems
Namespace Prefix:	mfin_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-20

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-20

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of nonaccrual financing receivable balance outstanding that is past due.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualPercentPastDue1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 49
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-49

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-18

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-18

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates title and position of individual or name of group identified as chief operating decision maker (CODM) for segment reporting.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

+ Details

Name:	us-gaap_SegmentReportingCodmIndividualTitleAndPositionOrGroupOrCommitteeNameExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of how chief operating decision maker (CODM) uses reported segment profit (loss) measure to assess performance and allocate resource.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (bb)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

+ Details

Name:	us-gaap_SegmentReportingCodmProfitLossMeasureHowUsedDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration