Acquisitions (Schedule of Revenues and Net Income from Continuing Operations) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Revenue	$ 54,872,000	$ 42,777,000	[1]
Net income from continuing operations	$ 3,196,000	4,284,000	[1]
Weeden Prime Services LLC [Member]
Business Acquisition [Line Items]
Revenue		968,000
Net income from continuing operations		$ 203,000

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