Revenue Recognition (Schedule of Major Revenue Categories) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Trading Execution and Clearing Services
Commissions and fees	$ 8,302,000	$ 9,504,000
Principal transactions	8,061,000	9,020,000
Advisory fees	801,000	478,000
Total Trading Execution and Clearing Services	17,164,000	19,002,000
Margin interest, marketing and distribution fees
Margin interest	8,134,000	7,663,000
12b1 fees	2,987,000	3,265,000
Total Margin interest, marketing and distribution fees	11,121,000	10,928,000
Interest and other income	308,000	106,000
Total Other Income	11,429,000	11,034,000
Total revenue	$ 28,593,000	$ 30,036,000