Debt - Additional Information (Detail) - Senior Revolving Credit Facility [Member]	9 Months Ended
Sep. 30, 2015 USD ($)
Line of Credit Facility [Line Items]
Secured line of credit	$ 538,000,000
Debt agreement expiration date	Sep. 18, 2018
Line of credit facility, accordion feature	$ 600,000,000
Unused line fee per annum	0.50%
Decrease in unused line fee	0.375%
Credit facility, eligible capacity	$ 81,787,000
Percentage of advances on debt agreement eligible secured finance receivables	85.00%
Percentage of advances on debt agreement eligible unsecured finance receivables	70.00%
Current percentage of advances on eligible secured finance receivables	83.00%
Current percentage of advances on eligible unsecured finance receivables	68.00%
Senior Revolving Credit Facility Prior To September 18, 2015 [Member]
Line of Credit Facility [Line Items]
Secured line of credit	$ 500,000,000
Debt agreement expiration date	May 13, 2016
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Senior Secured Revolving Credit Facility, Description of Variable Rate Basis	The Company elects between one and six months, with a LIBOR floor of 1.00%, plus a 3.00% margin.
Interest rate, basis spread	3.00%
Minimum effective interest rate on line of credit	1.00%
Base Rate [Member]
Line of Credit Facility [Line Items]
Senior Secured Revolving Credit Facility, Description of Variable Rate Basis	The Company may pay interest at a base rate plus 2.00% margin.
Interest rate, basis spread	2.00%

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

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	rm_
Data Type:	num:percentItemType
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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

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Namespace Prefix:	rm_
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Balance Type:	na
Period Type:	instant

- Definition

The amount by which the borrowing capacity of the line of credit facility may be expanded.

+ References

No definition available.

+ Details

Name:	rm_LineOfCreditFacilityAccordionFeature
Namespace Prefix:	rm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The decreased fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility at higher usage levels.

+ References

No definition available.

+ Details

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Namespace Prefix:	rm_
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Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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- Definition

When presenting a range of interest rates, the lowest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

+ 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)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:dateItemType
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

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	duration

- Details

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- Details

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- Details

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