Loans and Allowance for Credit Losses - Summary of Allowance for Credit Losses by Type (Parenthetical) (Detail)	Mar. 31, 2026	Dec. 31, 2025
Receivables [Abstract]
Allowance as a Percent of Nonaccrual	316.00%	281.00%

Allowance for loan and lease losses loans acquired percentage of loans nonaccrual.

No definition available.

Name:	mfin_AllowanceForLoanAndLeaseLossesLoansAcquiredPercentageOfLoansNonaccrual
Namespace Prefix:	mfin_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant