Financial Instruments with Off-Balance Sheet Risk (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financial Instruments With Off-balance-sheet Risk And Concentrations Of Credit Risk
Margin loans extended	$ 500.0	$ 600.0
Receivables from customers	$ 76.2	$ 84.2

Amount due from customers for fees and charges arising from transactions related to the entity's brokerage activities and operations.

No definition available.

Name:	SIEB_ReceivablesFromCustomers1
Namespace Prefix:	SIEB_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant