Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Financing Receivable Credit Quality Indicators (Detail) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	$ 1,190,235	$ 1,253,168
2024	586,482	433,924
2023	190,748	160,271
2022	70,733	40,215
2021	13,628	4,188
Prior	1,191	769
Total Net Finance Receivables	2,053,017	1,892,535	$ 1,819,756
FICO Band 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	159,466	154,585
2024	67,558	49,655
2023	22,400	14,194
2022	6,771	4,207
2021	1,964	833
Prior	507	401
Total Net Finance Receivables	258,666	223,875
FICO Band 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	87,860	88,062
2024	38,275	25,263
2023	10,288	6,926
2022	2,907	1,663
2021	559	177
Prior	73	94
Total Net Finance Receivables	139,962	122,185
FICO Band 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	140,969	143,488
2024	62,297	45,233
2023	18,910	17,640
2022	7,425	4,300
2021	1,189	343
Prior	78	61
Total Net Finance Receivables	230,868	211,065
FICO Band 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	177,404	193,067
2024	85,685	65,467
2023	28,304	26,682
2022	11,667	6,234
2021	1,835	579
Prior	126	107
Total Net Finance Receivables	305,021	292,136
FICO Band 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	189,962	212,701
2024	100,925	75,486
2023	32,151	30,064
2022	13,478	8,217
2021	2,847	787
Prior	150	39
Total Net Finance Receivables	339,513	327,294
FICO Band 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	434,574	461,265
2024	231,742	172,820
2023	78,695	64,765
2022	28,485	15,594
2021	5,234	1,469
Prior	257	67
Total Net Finance Receivables	778,987	715,980
Large Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	825,554	796,453
2024	430,940	344,308
2023	171,534	151,595
2022	69,451	39,578
2021	13,497	4,123
Prior	1,164	723
Total Net Finance Receivables	1,512,140	1,336,780	1,293,410
Large Loans [Member] \| FICO Band 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	92,736	86,776
2024	47,407	37,750
2023	19,246	12,457
2022	6,346	3,950
2021	1,887	793
Prior	489	373
Total Net Finance Receivables	168,111	142,099
Large Loans [Member] \| FICO Band 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	57,464	55,211
2024	28,315	19,464
2023	8,938	6,171
2022	2,790	1,602
2021	552	173
Prior	73	92
Total Net Finance Receivables	98,132	82,713
Large Loans [Member] \| FICO Band 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	94,171	90,642
2024	46,581	35,777
2023	17,004	16,579
2022	7,255	4,224
2021	1,176	339
Prior	77	59
Total Net Finance Receivables	166,264	147,620
Large Loans [Member] \| FICO Band 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	124,157	125,867
2024	65,001	52,564
2023	25,767	25,521
2022	11,495	6,140
2021	1,826	570
Prior	121	100
Total Net Finance Receivables	228,367	210,762
Large Loans [Member] \| FICO Band 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	136,430	137,243
2024	74,676	58,604
2023	28,733	28,564
2022	13,309	8,148
2021	2,836	784
Prior	149	36
Total Net Finance Receivables	256,133	233,379
Large Loans [Member] \| FICO Band 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	320,596	300,714
2024	168,960	140,149
2023	71,846	62,303
2022	28,256	15,514
2021	5,220	1,464
Prior	255	63
Total Net Finance Receivables	595,133	520,207
Small Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	364,681	456,715
2024	155,542	89,616
2023	19,214	8,676
2022	1,282	637
2021	131	65
Prior	27	46
Total Net Finance Receivables	540,877	555,755	$ 526,346
Small Loans [Member] \| FICO Band 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	66,730	67,809
2024	20,151	11,905
2023	3,154	1,737
2022	425	257
2021	77	40
Prior	18	28
Total Net Finance Receivables	90,555	81,776
Small Loans [Member] \| FICO Band 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	30,396	32,851
2024	9,960	5,799
2023	1,350	755
2022	117	61
2021	7	4
Prior	0	2
Total Net Finance Receivables	41,830	39,472
Small Loans [Member] \| FICO Band 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	46,798	52,846
2024	15,716	9,456
2023	1,906	1,061
2022	170	76
2021	13	4
Prior	1	2
Total Net Finance Receivables	64,604	63,445
Small Loans [Member] \| FICO Band 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	53,247	67,200
2024	20,684	12,903
2023	2,537	1,161
2022	172	94
2021	9	9
Prior	5	7
Total Net Finance Receivables	76,654	81,374
Small Loans [Member] \| FICO Band 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	53,532	75,458
2024	26,249	16,882
2023	3,418	1,500
2022	169	69
2021	11	3
Prior	1	3
Total Net Finance Receivables	83,380	93,915
Small Loans [Member] \| FICO Band 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025	113,978	160,551
2024	62,782	32,671
2023	6,849	2,462
2022	229	80
2021	14	5
Prior	2	4
Total Net Finance Receivables	$ 183,854	$ 195,773

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: