Quarterly report pursuant to sections 13 or 15(d)

Securities Owned and Securities Sold, But Not Yet Purchased - at Fair Value (Details)

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Securities Owned and Securities Sold, But Not Yet Purchased - at Fair Value (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned $ 3,834 $ 2,078
Securities sold, but not yet purchased (333) (292)
Debt securities
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 1,666 1,098
Securities sold, but not yet purchased (15) (123)
Certificates of deposit
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned   14
Securities sold, but not yet purchased   0
U.S. Treasury notes
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 5 0
Securities sold, but not yet purchased (198) (99)
Common stock and warrants
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 1,555 384
Securities sold, but not yet purchased (120) (70)
Restricted common stock and warrants
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 608 582
Securities sold, but not yet purchased $ 0 $ 0