Annual report pursuant to section 13 and 15(d)

Securities Owned and Securities Sold, But Not Yet Purchased (Components of Securities Owned and Securities Sold, but not yet Purchased) (Details)

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Securities Owned and Securities Sold, But Not Yet Purchased (Components of Securities Owned and Securities Sold, but not yet Purchased) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned $ 4,789 $ 2,078
Securities Sold,But Not Yet Purchased (83) (292)
Certificates of Deposit [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned 24 14
Securities Sold,But Not Yet Purchased 0 0
Debt Securities [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned 1,402 1,098
Securities Sold,But Not Yet Purchased (46) (123)
U.S. Treasury Notes [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned 1 0
Securities Sold,But Not Yet Purchased 0 (99)
Common Stock and Warrants [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned 689 384
Securities Sold,But Not Yet Purchased (33) (70)
Restricted Common Stock and Warrants [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned 725 582
Securities Sold,But Not Yet Purchased (4) 0
Other Investments [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned 1,948  
Securities Sold,But Not Yet Purchased $ 0