Securities Owned and Sold, Not Yet Purchased (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012
Securities owned and sold, not yet purchased.
Securities owned, at fair value	$ 5,277,000	$ 10,086,000
Securities sold, not yet purchased, at fair value	438,000	5,249,000
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	689,000	5,438,000
Securities sold, not yet purchased, at fair value	438,000	5,249,000
Mutual funds
Securities owned and sold, not yet purchased.
Securities owned, at fair value	$ 4,588,000	$ 4,648,000