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) (Detail)

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Securities Owned and Securities Sold, But Not Yet Purchased (Components Of Securities Owned And Securities Sold) (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned $ 2,078 $ 2,014
Securities sold, but not yet purchased 292 78
Common Stock and Warrants [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 384 191
Securities sold, but not yet purchased 70 78
Common Stock and Warrants [Member] | Components
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 384 191
Securities sold, but not yet purchased (70) (78)
Restricted common stock and warrants
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 582 1,823
Securities sold, but not yet purchased 0 0
Restricted common stock and warrants | Components
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 582 1,823
Securities sold, but not yet purchased 0 0
Us Treasury Notes Securities [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 0  
Securities sold, but not yet purchased 99  
Us Treasury Notes Securities [Member] | Components
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 0  
Securities sold, but not yet purchased (99)  
Debt Securities [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 1,098  
Securities sold, but not yet purchased 123  
Debt Securities [Member] | Components
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 1,098  
Securities sold, but not yet purchased (123)  
Certificates Of Deposit [Member]
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 14  
Securities sold, but not yet purchased 0  
Certificates Of Deposit [Member] | Components
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned 14  
Securities sold, but not yet purchased $ 0