8. Investment in and advances to affiliates (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Siebert, Brandford, Shank & Co., L.L.C. [Member]	Jun. 30, 2012 Siebert, Brandford, Shank & Co., L.L.C. [Member]
Total assets, including secured demand note of $1,200,000 due from Siebert			$ 18,224,000
Total liabilities, including subordinated liabilities of $1,200,000 due to Siebert			4,442,000
Total members' capital			13,782,000
Regulatory minimum net capital requirement			250,000
Total revenues	5,034,000	8,428,000	9,028,000	14,054,000
Net income (loss)	$ (713,000)	$ 1,730,000	$ (1,941,000)	$ 1,432,000