Annual report pursuant to Section 13 and 15(d)

Securities Owned and Securities Sold, But Not Yet Purchased (Narrative) (Details)

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Securities Owned and Securities Sold, But Not Yet Purchased (Narrative) (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned deposited with the Company's subsidiaries clearing broker $ 3,383 $ 5,429
Securities owned at fair value 4,079 5,910
Level 2    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned at fair value 2,793 3,464
Common Stock and Warrants    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned at fair value 927 1,981
Common Stock and Warrants | Warrants to purchase common stock | Level 2    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned at fair value $ 545 $ 403