8. Investment In and Advances to Affiliates (Details) (Siebert Brandford Shank Co LLC [Member], USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Siebert Brandford Shank Co LLC [Member]
Total assets, including secured demand note of $1,200,000 due from Siebert	$ 26,480,000
Total liabilities, including subordinated liabilities of $1,200,000 due to Siebert	11,972,000
Total members' capital	14,508,000
Regulatory minimum net capital requirement	250,000
Total revenues	4,049,000	7,735,000
Net income (loss)	$ (1,521,000)	$ 1,481,000