Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Name:	us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Equity Method Investments (Narrative) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Loss from equity method investment in related party		$ (66,000)
StockCross [Member]
Percentage of outstanding shares purchased by company		15.00%
Shares purchased		922,875
Per share price		$ 3.97
Capital distribution	$ 1,600,000
StockCross [Member] \| Siebert [Member]
Capital distribution	$ 241,000