Securities Owned and Sold, Not Yet Purchased (Details) (USD $)	3 Months Ended	9 Months Ended
	Mar. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Securities owned and sold, not yet purchased
Securities owned, at fair value		$ 5,890,000	$ 25,789,000
Securities sold, not yet purchased, at fair value		1,395,000	19,362,000
After-Tax Unrealized Holding Gain/(Loss)
Positions with net gains			86,000
Total gain/(loss)			86,000
Gross proceeds from the sale of available-for-sale securities	2,100,000
Pre-tax gain on the sale of available-for-sale securities		500,000
Corporate stocks - trading securities
Securities owned and sold, not yet purchased
Securities owned, at fair value		1,348,000	19,051,000
Securities sold, not yet purchased, at fair value		1,395,000	19,362,000
Corporate stocks - available-for-sale
Securities owned and sold, not yet purchased
Securities owned, at fair value			1,662,000
Mutual funds
Securities owned and sold, not yet purchased
Securities owned, at fair value		$ 4,542,000	$ 5,076,000