Fair Value Measurements (Schedule of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value) (Details) - USD ($)		Sep. 30, 2022	Dec. 31, 2021
Assets
Securities owned, at fair value		$ 3,468,000	$ 3,991,000
Liabilities
Securities sold, not yet purchased, at fair value		11,000	24,000
Equity Securities [Member]
Assets
Securities owned, at fair value			922,000
Liabilities
Securities sold, not yet purchased, at fair value		4,000	24,000
Level 1 [Member]
Assets
Securities owned, at fair value		2,919,000	3,455,000
Liabilities
Securities sold, not yet purchased, at fair value		4,000
Level 1 [Member] | Equity Securities [Member]
Assets
Securities owned, at fair value		96,000	489,000
Liabilities
Securities sold, not yet purchased, at fair value		4,000
Level 2 [Member]
Assets
Securities owned, at fair value		549,000	536,000
Liabilities
Securities sold, not yet purchased, at fair value		7,000	24,000
Level 2 [Member] | Equity Securities [Member]
Assets
Securities owned, at fair value		177,000	433,000
Liabilities
Securities sold, not yet purchased, at fair value			24,000
Level 3 [Member]
Assets
Securities owned, at fair value
Liabilities
Securities sold, not yet purchased, at fair value
Level 3 [Member] | Equity Securities [Member]
Assets
Securities owned, at fair value
Liabilities
Securities sold, not yet purchased, at fair value
U.S. government securities [Member]
Assets
Cash and securities segregated for regulatory purposes	[1]	140,197,000
Securities owned, at fair value	[2]	2,823,000	2,966,000
U.S. government securities [Member] | Level 1 [Member]
Assets
Cash and securities segregated for regulatory purposes	[1]	140,197,000
Securities owned, at fair value	[2]	2,823,000	2,966,000
U.S. government securities [Member] | Level 2 [Member]
Assets
Cash and securities segregated for regulatory purposes
Securities owned, at fair value
U.S. government securities [Member] | Level 3 [Member]
Assets
Cash and securities segregated for regulatory purposes
Securities owned, at fair value
Certificates of Deposit [Member]
Assets
Securities owned, at fair value		92,000	91,000
Certificates of Deposit [Member] | Level 1 [Member]
Assets
Securities owned, at fair value
Certificates of Deposit [Member] | Level 2 [Member]
Assets
Securities owned, at fair value		92,000	91,000
Certificates of Deposit [Member] | Level 3 [Member]
Assets
Securities owned, at fair value
Municipal securities [Member]
Assets
Securities owned, at fair value		174,000
Municipal securities [Member] | Level 1 [Member]
Assets
Securities owned, at fair value
Municipal securities [Member] | Level 2 [Member]
Assets
Securities owned, at fair value		174,000
Municipal securities [Member] | Level 3 [Member]
Assets
Securities owned, at fair value
Corporate bonds [Member]
Assets
Securities owned, at fair value		106,000	12,000
Corporate bonds [Member] | Level 1 [Member]
Assets
Securities owned, at fair value
Corporate bonds [Member] | Level 2 [Member]
Assets
Securities owned, at fair value		106,000	12,000
Corporate bonds [Member] | Level 3 [Member]
Assets
Securities owned, at fair value
Unit investment trust [Member]
Liabilities
Securities sold, not yet purchased, at fair value		7,000
Unit investment trust [Member] | Level 1 [Member]
Liabilities
Securities sold, not yet purchased, at fair value
Unit investment trust [Member] | Level 2 [Member]
Liabilities
Securities sold, not yet purchased, at fair value		7,000
Unit investment trust [Member] | Level 3 [Member]
Liabilities
Securities sold, not yet purchased, at fair value

[1] As of September 30, 2022, the Company had U.S. government securities with market values of approximately $24.6 million, $9.8million, $9.7 million, $62.2 million, $23.9 million, and $9.7 million with corresponding maturity dates of March 23, 2023, May 18, 2023, August 31, 2023, December 31, 2023, January 31, 2024, and May 31, 2024, respectively as well as approximately $0.3 million of interest. As of December 31, 2021, the Company did not have any U.S. government securities classified as cash and securities segregated for regulatory purposes.

[2] As of September 30, 2022, the Company had U.S. government securities with market values of approximately $24,000, $5,000 and $2.8 million with corresponding maturity dates of June 30, 2024, September 30, 2024, and August 15, 2024, respectively. As of December 31, 2021, the U.S. government securities had a maturity date of August 15, 2024.