Revenue Recognition (Schedule of Major Revenue Categories) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Trading Execution and Clearing Services
Commissions and fees	$ 18,252,000	$ 20,179,000
Principal transactions	15,647,000	11,850,000
Market making	5,897,000	2,042,000
Stock borrow / stock loan	11,864,000	4,045,000
Advisory fees	1,668,000	1,142,000
Total Trading Execution and Clearing Services	53,328,000	39,258,000
Interest, marketing and distribution fees
Interest	3,619,000	4,012,000
Margin interest	8,618,000	8,725,000
12b-1 fees	660,000	1,458,000
Total Interest, marketing and distribution fees	12,897,000	14,195,000
Other income	1,282,000	1,419,000
Total Revenue	$ 67,507,000	$ 54,872,000