Quarterly report pursuant to Section 13 or 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
Jun. 30, 2016
Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned deposited with the Company's subsidiaries clearing broker $ 3,084 $ 3,383
Securities owned, at fair value 3,763 4,079
Common stock and warrants    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned, at fair value 491 927
Level 2    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned, at fair value 2,946 2,793
Level 2 | Common stock and warrants | Warrants to purchase common stock    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities owned, at fair value $ 523 $ 545