Expense for self-insurance claims.

No definition available.

Name:	SIEB_ExpenseForSelfInsuranceClaims
Namespace Prefix:	SIEB_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Health claim reinsurance limit per employee.

+ References

No definition available.

+ Details

Name:	SIEB_HealthClaimReinsuranceLimitPerEmployee
Namespace Prefix:	SIEB_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Offer of rescission of commissions.

+ References

No definition available.

+ Details

Name:	SIEB_OfferOfRescissionOfCommissions
Namespace Prefix:	SIEB_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

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+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

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

- 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

- Definition

Amount of loss contingency liability expected to be resolved within one year or the normal operating cycle, if longer.

+ References

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+ Details

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

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

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

- Definition

Amount of general and administrative expense classified as other.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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+ Details

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

- Definition

Amount paid to managing member or general partner, affiliate of managing member or general partner, or affiliate of limited liability company (LLC) or limited partnership (LP) for administrative services provided to the LLC or LP, for example, but not limited to, salaries, rent, or overhead costs.

+ References

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+ Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=SIEB_MSCOMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=SIEB_AccrualOfFINRAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=SIEB_AccrualOfCaliforniaAdministrativeCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_LitigationCaseAxis=SIEB_FinraRequirementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=SIEB_MSCOMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_LitigationCaseAxis=SIEB_SupervisoryRequirementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=SIEB_StockCrossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=SIEB_CaliforniaDepartmentOfFinancialProtectionandInnovationMember
Namespace Prefix:
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Balance Type:
Period Type:

Commitments, Contingencies, and Other (Narrative) (Details) - USD ($)			3 Months Ended			9 Months Ended
	Jul. 14, 2021	Jul. 09, 2021	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Health claim reinsurance limit per employee			$ 65,000			$ 65,000
Expense for self-insurance claims			404,000		$ 412,000	1,054,000	$ 962,000
Accrual for self-insurance claims			102,000			102,000
Interest expense			52,000		74,000	156,000	220,000
Other general and administrative expense			927,000		455,000	2,885,000	1,710,000
BMO Harris Bank and Texas Capital Bank [Member]
Available lines of credit			15,000,000			15,000,000
Interest expense			$ 0		$ 0	$ 15,000	$ 18,000
BMO Harris Bank [Member] \| MSCO [Member]
Line of credit								$ 15,000,000
Texas Capital Bank [Member] \| MSCO [Member]
Line of credit								$ 15,000,000
Accrual of FINRA [Member]
Other general and administrative expense				$ 250,000
Accrual of California administrative costs [Member]
Other general and administrative expense				$ 100,000
FINRA Requirements [Member] \| MSCO [Member]
Aggregate amount in legal matters	$ 250,000
Supervisory Requirements [Member] \| StockCross [Member] \| California Department of Financial Protection and Innovation [Member]
Payment of administrative costs		$ 100,000
Offer of rescission of commissions		$ 315,000