Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 01, 2021	Jun. 30, 2020
Document And Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Entity File Number	0-5703
Entity Registrant Name	Siebert Financial Corp
Entity Incorporation State Country Code	NY
Entity Tax Identification Number	11-1796714
Entity Address, Address Line One	120 Wall Street
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10005
City Area Code	212
Local Phone Number	644-2400
Title of 12(b) Security	Common Stock - $0.01 par value
Trading Symbol	SIEB
Name of Exchange on which Security is Registered	NASDAQ
Is Entity a Well-known Seasoned Issuer?	No
Is Entity a Voluntary Filer?	No
Is Entity's Reporting Status Current?	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 43,170,000
Entity Common Stock, Shares Outstanding		31,283,364
Auditor Attestation Flag	true
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000065596
Current Fiscal Year End Date	--12-31