Quarterly report pursuant to sections 13 or 15(d)

Securities Carried at Fair value (Detail)

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Securities Carried at Fair value (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2012
Dec. 31, 2011
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value $ 1,132 $ 2,014
Securities sold, but not yet purchased 87 78
Fair Value, Inputs, Level 1
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities sold, but not yet purchased 76 68
Fair Value, Inputs, Level 2
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities sold, but not yet purchased 11 10
Common stock and warrants
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value 177 191
Securities sold, but not yet purchased 87 78
Common stock and warrants | Fair Value, Inputs, Level 1
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities sold, but not yet purchased 76 68
Common stock and warrants | Fair Value, Inputs, Level 2
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities sold, but not yet purchased 11 10
Portion at Fair Value, Fair Value Disclosure
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value 1,132 2,014
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 1
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value 177 191
Portion at Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value 955 1,823
Portion at Fair Value, Fair Value Disclosure | Common stock and warrants
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value 1,132 2,014
Portion at Fair Value, Fair Value Disclosure | Common stock and warrants | Fair Value, Inputs, Level 1
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value 177 191
Portion at Fair Value, Fair Value Disclosure | Common stock and warrants | Fair Value, Inputs, Level 2
    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities owned at fair value $ 955 $ 1,823