Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Financing Receivable Credit Quality Indicators (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	$ 373,144	$ 1,497,721
2025	1,238,940	436,202
2024	336,305	143,973
2023	110,592	52,423
2022	38,526	9,079
Prior	6,494	801
Total Net Finance Receivables	2,104,001	2,140,199	$ 1,890,351
FICO Band 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	56,570	202,359
2025	165,569	49,218
2024	37,838	17,162
2023	13,074	5,301
2022	4,192	1,509
Prior	1,474	395
Total Net Finance Receivables	278,717	275,944
FICO Band 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	29,153	111,790
2025	91,649	27,587
2024	21,112	7,637
2023	5,866	2,148
2022	1,587	385
Prior	294	48
Total Net Finance Receivables	149,661	149,595
FICO Band 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	42,644	175,021
2025	142,686	44,967
2024	34,340	14,199
2023	11,045	5,495
2022	4,009	747
Prior	502	51
Total Net Finance Receivables	235,226	240,480
FICO Band 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	53,491	223,052
2025	183,097	62,956
2024	48,281	21,530
2023	16,575	8,664
2022	6,456	1,134
Prior	783	80
Total Net Finance Receivables	308,683	317,416
FICO Band 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	56,883	237,016
2025	196,331	75,137
2024	57,577	24,089
2023	18,572	10,086
2022	7,357	1,898
Prior	1,319	91
Total Net Finance Receivables	338,039	348,317
FICO Band 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	134,403	548,483
2025	459,608	176,337
2024	137,157	59,356
2023	45,460	20,729
2022	14,925	3,406
Prior	2,122	136
Total Net Finance Receivables	793,675	808,447
Large Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	257,232	1,061,776
2025	912,434	336,199
2024	272,058	133,686
2023	105,258	51,732
2022	38,129	8,995
Prior	6,417	783
Total Net Finance Receivables	1,591,528	1,593,171	1,345,825
Large Loans [Member] \| FICO Band 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	30,525	119,724
2025	104,813	36,692
2024	29,643	15,225
2023	11,862	5,034
2022	4,022	1,453
Prior	1,423	382
Total Net Finance Receivables	182,288	178,510
Large Loans [Member] \| FICO Band 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	18,984	75,189
2025	64,410	21,423
2024	17,126	6,854
2023	5,431	2,086
2022	1,555	383
Prior	292	48
Total Net Finance Receivables	107,798	105,983
Large Loans [Member] \| FICO Band 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	28,753	121,142
2025	103,349	35,473
2024	28,501	13,157
2023	10,480	5,398
2022	3,952	739
Prior	494	51
Total Net Finance Receivables	175,529	175,960
Large Loans [Member] \| FICO Band 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	38,284	160,692
2025	136,967	50,359
2024	40,628	20,102
2023	15,809	8,588
2022	6,415	1,130
Prior	779	77
Total Net Finance Receivables	238,882	240,948
Large Loans [Member] \| FICO Band 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	41,321	173,379
2025	148,529	58,320
2024	46,981	22,357
2023	17,737	9,995
2022	7,304	1,893
Prior	1,314	90
Total Net Finance Receivables	263,186	266,034
Large Loans [Member] \| FICO Band 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	99,365	411,650
2025	354,366	133,932
2024	109,179	55,991
2023	43,939	20,631
2022	14,881	3,397
Prior	2,115	135
Total Net Finance Receivables	623,845	625,736
Small Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	115,912	435,945
2025	326,506	100,003
2024	64,247	10,287
2023	5,334	691
2022	397	84
Prior	77	18
Total Net Finance Receivables	512,473	547,028	$ 544,526
Small Loans [Member] \| FICO Band 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	26,045	82,635
2025	60,756	12,526
2024	8,195	1,937
2023	1,212	267
2022	170	56
Prior	51	13
Total Net Finance Receivables	96,429	97,434
Small Loans [Member] \| FICO Band 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	10,169	36,601
2025	27,239	6,164
2024	3,986	783
2023	435	62
2022	32	2
Prior	2	0
Total Net Finance Receivables	41,863	43,612
Small Loans [Member] \| FICO Band 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	13,891	53,879
2025	39,337	9,494
2024	5,839	1,042
2023	565	97
2022	57	8
Prior	8	0
Total Net Finance Receivables	59,697	64,520
Small Loans [Member] \| FICO Band 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	15,207	62,360
2025	46,130	12,597
2024	7,653	1,428
2023	766	76
2022	41	4
Prior	4	3
Total Net Finance Receivables	69,801	76,468
Small Loans [Member] \| FICO Band 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	15,562	63,637
2025	47,802	16,817
2024	10,596	1,732
2023	835	91
2022	53	5
Prior	5	1
Total Net Finance Receivables	74,853	82,283
Small Loans [Member] \| FICO Band 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2026	35,038	136,833
2025	105,242	42,405
2024	27,978	3,365
2023	1,521	98
2022	44	9
Prior	7	1
Total Net Finance Receivables	$ 169,830	$ 182,711

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

+ Details

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

- Definition

Amortized cost of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

+ Details

Name:	us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477011/948-310-45-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-13

Reference 5: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A

Reference 6: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-29

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (1)
-Publisher SEC

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (2)
-Publisher SEC

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Regulation S-K (SK)
-Number 229
-Section 1404
-Paragraph a
-Publisher SEC

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 80
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-80

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-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

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_NotesReceivableGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=rm_Grade1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=rm_Grade2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=rm_Grade3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=rm_Grade4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=rm_Grade5Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=rm_Grade6Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rm_LargeLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rm_SmallLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: