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Marketable Securities (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014 | Dec. 31, 2014
Schedule of Investments [Line Items] |  |  |  |  |
Net unrealized gains | $ 32 |  | $ 32 |  | $ 1,193
Unrealized gains during the period, income tax expense | 251 |  | 251 |  | 703
Available-for-sale securities, gross realized gains |  |  | 394 | $ 238 |
Available-for-sale securities, gross realized losses |  |  | 535 | 247 |
Investment funds sponsored by LSV | 3,944 |  | 3,944 |  | 4,523
Securities owned | 21,225 |  | 21,225 |  | 21,175
Private Equity Funds, Foreign [Member] |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |
Investment funds sponsored by LSV | 3,944 |  | 3,944 |  | $ 4,523
Realized gains (losses) from investment funds sponsored by LSV | $ (581) | $ (362) | $ (579) | $ 59 |

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