Receivables from and Payables to Brokers, Dealers, and Clearing Organizations (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Receivables from and Payables to Brokers, Dealers, and Clearing Organizations
Deposits with clearing organizations	$ 8,266,000	$ 9,566,000
Receivable from clearing organizations	3,715,000	2,001,000
Receivable for unsettled trading activities	1,094,000	237,000
Underwriting and syndicate fees receivable	362,000	1,020,000
Total receivables	13,437,000	12,824,000
Payable to clearing organizations	408,666,000	638,009,000
Payable for unsettled trading activities	547,000
Total payables	409,213,000	638,009,000
Deposit with FICC	6,300,000	8,800,000
Excess equity held at the entity's principal clearing broker	$ 37,600,000	$ 35,500,000