Fair Value of Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
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| Schedule of Trading Securities and Other Trading Assets [Line Items] | ||
| Securities owned deposited with the Company's subsidiaries clearing broker | $ 3,239 | $ 3,265 |
| Securities owned, at fair value | 4,104 | 3,881 |
| 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 | $ 717 | $ 475 |
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- Definition Securities owned and held at clearing broker. No definition available.
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition Fair value of financial instruments held by a broker-dealer for their own account (proprietary securities) for trading or investment purposes determined by management based upon quoted prices of a financial instrument with similar characteristics or on a valuation technique or model. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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