Refers to as a desription of line of credit facility success fees.

No definition available.

Name:	rily_LineOfCreditFacilitySuccessFeeDescription
Namespace Prefix:	rily_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

It refers to the amount of payment for closing fee.

+ References

No definition available.

+ Details

Name:	rily_PaymentForClosingFee
Namespace Prefix:	rily_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

Name:	us-gaap_InterestExpenseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Discussion of whether the borrowings under the credit facility are secured or unsecured and, if secured, a description of collateral (for example, accounts receivable less than 120 days old, finished goods inventory).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

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

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

+ Details

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

- 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

+ Details

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

- Details

Name:	srt_TitleOfIndividualAxis=rily_ClearingOrganisationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=rily_SecondAmendedAndRestatedCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=rily_AssetBasedCreditFacility100000Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=rily_WellsFargoBankNationalAssociationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=rily_UKCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Notes Payable (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
Notes Payable (Details) - USD ($) $ in Thousands	Apr. 21, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 19, 2015
Interest expense		$ 43,823	$ 25,428	$ 6,390
Clearing Organisation [Member]
Description of interest rate					The notes payable accrue interest at the prime rate plus 2.0% (7.5% at December 30, 2019) payable annually, maturing January 31, 2022.
Interest expense					$ 87	$ 111	$ 71
Credit facility		1,071	1,550		1,071	1,550
Second Amended and Restated Credit Agreement [Member] \| Asset Based Credit Facility [Member] \| Wells Fargo Bank, National Association [Member]
Credit facility expiration date	Apr. 21, 2022
Description of interest rate	The interest rate for each revolving credit advance under the Credit Agreement is, subject to certain terms and conditions, equal to the LIBOR plus a margin of 2.25% to 3.25% depending on the type of advance and the percentage such advance represents of the related transaction for which such advance is provided.
Description of success fees	The credit facility also provides for success fees in the amount of 2.5% to 17.5% of the net profits, if any, earned on the liquidation engagements funded under the Credit Agreement as set forth therein.
Interest expense					1,503	4,247	$ 1,136
Description of collateral	The credit facility is secured by the proceeds received for services rendered in connection with liquidation service contracts pursuant to which any outstanding loan or letters of credit are issued and the assets that are sold at liquidation related to such contract.
Payment for closing fee	$ 500
Credit facility		$ 37,096	$ 0		$ 37,096	$ 0
Second Amended and Restated Credit Agreement [Member] \| Asset Based Credit Facility [Member] \| Wells Fargo Bank, National Association [Member] \| Maximum [Member]
Maximum borrowing capacity credit facility	200
Second Amended and Restated Credit Agreement [Member] \| Asset Based Credit Facility [Member] \| Wells Fargo Bank, National Association [Member] \| Minimum [Member]
Maximum borrowing capacity credit facility	$ 100
UK Credit Agreement [Member]
Credit facility								$ 200
UK Credit Agreement [Member] \| Line of Credit [Member] \| Wells Fargo Bank, National Association [Member]
Maximum borrowing capacity credit facility								$ 500