Notes Payable - Related Party (Schedule of Notes Payable) (Details) - USD ($)		6 Months Ended
		Jun. 30, 2020	Dec. 31, 2019	[1]
Short-term Debt [Line Items]
Notes payable - related party		$ 8,000,000	$ 8,000,000
Subordinated to MSCO [Member]
Short-term Debt [Line Items]
Notes payable - related party	[2]	$ 5,000,000
4% due December 2, 2020 [Member]
Short-term Debt [Line Items]
Issuance Date		Dec. 02, 2019
Notes payable - related party		$ 3,000,000
4% due November 30, 2020 [Member] | Subordinated to MSCO [Member]
Short-term Debt [Line Items]
Issuance Date	[2],[3]	Nov. 30, 2018
Notes payable - related party	[2],[3]	$ 3,000,000
4% due September 4, 2020 [Member] | Subordinated to MSCO [Member]
Short-term Debt [Line Items]
Issuance Date	[2]	Sep. 04, 2019
Notes payable - related party	[2]	$ 2,000,000

[1] Statement of financial condition as of December 31, 2019 represents the pro forma combination of Siebert and StockCross balances. See "Note 3 - Acquisitions" for additional detail.

[2] The notes payable subordinated to MSCO were acquired as part of the acquisition of StockCross

[3] This note payable was renewed on November 30, 2019 for a term of one year