The standard percentage of eligible secured finance receivables that is available to be advanced from credit facility.

No definition available.

Name:	rm_AdvancesOnDebtAgreementEligibleSecuredFinanceReceivables
Namespace Prefix:	rm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The standard percentage of eligible unsecured finance receivables that is available to be advanced from credit facility.

+ References

No definition available.

+ Details

Name:	rm_AdvancesOnDebtAgreementEligibleUnsecuredFinanceReceivables
Namespace Prefix:	rm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The current period percentage of eligible secured finance receivables that is available to be advanced from credit facility.

+ References

No definition available.

+ Details

Name:	rm_CurrentPercentageOfAdvancesOnEligibleSecuredFinanceReceivables
Namespace Prefix:	rm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The current period percentage of eligible unsecured finance receivables that is available to be advanced from credit facility.

+ References

No definition available.

+ Details

Name:	rm_CurrentPercentageOfAdvancesOnEligibleUnsecuredFinanceReceivables
Namespace Prefix:	rm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The maturity date of the amortizing loan credit agreement, in CCYY-MM format.

+ References

No definition available.

+ Details

Name:	rm_DebtInstrumentMaturityDateOne
Namespace Prefix:	rm_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

The servicing fee percentage paid by the VIE to the servicer.

+ References

No definition available.

+ Details

Name:	rm_PercentageOfServiceFeeOnLoan
Namespace Prefix:	rm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AllowanceForDoubtfulAccountsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the payment terms of the debt instrument (for example, whether periodic payments include principal and frequency of payments) and discussion about any contingencies associated with the payment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

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

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524

+ Details

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

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

+ Details

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

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=rm_ContractualPriorityPaymentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rm_AssetBackedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=rm_CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Long-Term Debt - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Finance receivables	$ 696,149,000	$ 628,444,000		$ 601,608,000
Allowance for credit losses	39,100,000	37,452,000	$ 36,200,000	37,786,000	$ 36,171,000	$ 40,511,000
Cash deposited to restricted cash reserve account	7,906,000	10,506,000
Waterfall [Member]
Line of Credit Facility [Line Items]
Cash deposited to restricted cash reserve account	3,100,000
Variable Interest Entity, Primary Beneficiary [Member]
Line of Credit Facility [Line Items]
Finance receivables	49,608,000	80,309,000
Allowance for credit losses	2,976,000	2,588,000
Cash deposited to restricted cash reserve account	$ 4,786,000	7,605,000
Servicing fee	4.00%
Asset Backed Loans [Member]
Line of Credit Facility [Line Items]
Amortizing loan, amount		$ 75,700,000
Amortizing loan, maturity date		2022-12
Senior Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Current percentage of advances on eligible secured finance receivables	85.00%
Current percentage of advances on eligible unsecured finance receivables	70.00%
Percentage of advances on debt agreement eligible secured finance receivables	85.00%
Percentage of advances on debt agreement eligible unsecured finance receivables	70.00%
Credit facility, eligible capacity	$ 70,700,000
Credit Agreement [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Line of Credit Facility [Line Items]
Allowance for credit losses		$ 2,600,000
Cash deposited to restricted cash reserve account		$ 1,700,000
Credit agreement, Interest rate		3.00%
Terms related to loan prepayment	The credit agreement allows RMR to prepay the loan when the outstanding balance falls below 20% of the original loan amount.
Automobile Loans [Member]
Line of Credit Facility [Line Items]
Finance receivables	$ 97,141,000	$ 116,109,000		128,131,000
Allowance for credit losses	$ 6,500,000	8,828,000	$ 7,851,000	$ 10,293,000	$ 11,121,000	$ 11,776,000
Automobile Loans [Member] \| Credit Agreement [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Line of Credit Facility [Line Items]
Finance receivables		$ 86,100,000