Organization and Basis of Presentation (Policies)	3 Months Ended
Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements (“financial statements”) of the Company have been prepared in accordance with accounting principles generally accepted in the U.S. (“GAAP”) for interim financial information with the instructions for Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by GAAP for complete annual financial statements. In the opinion of management, the financial statements contain all adjustments (consisting of normal recurring entries) necessary to fairly present such interim results. Interim results are not necessarily indicative of the results of operations which may be expected for a full year or any subsequent period. These financial statements should be read in conjunction with the financial statements and notes thereto in the Company’s 2020 Form 10-K. The financial statements include the accounts of Siebert and its wholly-owned subsidiaries and upon consolidation, all intercompany balances and transactions are eliminated. The U.S. dollar is the functional currency of the Company and numbers are rounded for presentation purposes. Significant Accounting Policies The Company’s significant accounting policies are included in Note 2 – Summary of Significant Accounting Policies in the Company’s 2020 Form 10-K.
Investments, Cost	Investments, Cost Accounting Standards Update (“ASU”) 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, generally requires entities to measure equity investments (other than equity method investments, controlling financial interests that result in consolidation of the investee and certain other investments) at fair value and recognize any changes in fair value in net income. However, entities will be able to elect a measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the practical expedient in ASC 820 to estimate fair value using the net asset value (NAV) per share. Pursuant to ASU 2016-01, the Company has made an accounting policy election to measure equity securities without readily determinable fair value at cost, less any impairment, adjusted for any changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer.

Organization and Basis of Presentation (Policies)

3 Months Ended

Mar. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The accompanying condensed consolidated financial statements (“financial statements”) of the Company have been prepared in accordance with accounting principles generally accepted in the U.S. (“GAAP”) for interim financial information with the instructions for Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by GAAP for complete annual financial statements. In the opinion of management, the financial statements contain all adjustments (consisting of normal recurring entries) necessary to fairly present such interim results. Interim results are not necessarily indicative of the results of operations which may be expected for a full year or any subsequent period. These financial statements should be read in conjunction with the financial statements and notes thereto in the Company’s 2020 Form 10-K. The financial statements include the accounts of Siebert and its wholly-owned subsidiaries and upon consolidation, all intercompany balances and transactions are eliminated. The U.S. dollar is the functional currency of the Company and numbers are rounded for presentation purposes.

Significant Accounting Policies

The Company’s significant accounting policies are included in Note 2 – Summary of Significant Accounting Policies in the Company’s 2020 Form 10-K.

Investments, Cost

Accounting Standards Update (“ASU”) 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, generally requires entities to measure equity investments (other than equity method investments, controlling financial interests that result in consolidation of the investee and certain other investments) at fair value and recognize any changes in fair value in net income. However, entities will be able to elect a measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the practical expedient in ASC 820 to estimate fair value using the net asset value (NAV) per share.

Pursuant to ASU 2016-01, the Company has made an accounting policy election to measure equity securities without readily determinable fair value at cost, less any impairment, adjusted for any changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer.