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Securities Owned/Sold but Not Yet Purchased - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Proceeds from sale and maturity of available-for-sale securities | $ 0 |  | $ 64,498
Recognized gross realized losses |  |  | $ 739
Securities Owned and Securities Sold [Member] |  |  |
Trading losses on securities owned | $ 59 | $ 43 |

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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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- Definition Amount of cash inflow from sale, maturity, prepayment and call of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3151-108585 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26853-111562 + Details
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- Definition Unrealized profit and loss on trading securities held at the reporting date. + References No definition available. + Details
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- Details
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