MARGIN LENDING, BROKERAGE AND OTHER RECEIVABLES, NET - Narrative (Details) - USD ($) $ in Thousands  | 
Mar. 31, 2023  | 
Mar. 31, 2022  | 
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| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Securities loaned, fair value of collateral | $ 1,418,129 | $ 4,432,621 | 
| Related party transaction, brokerage and other receivable due from related party | $ 290,195 | $ 102,669 | 
| Brokerage and other receivables from Related party as a percentage of related party brokerage and other receivables | 78.00% | 73.00% | 
| Lending margin receivable | $ 37,100 | |
| Total margin lending, brokerage and other receivables, net | 376,329 | $ 147,659 | 
| Allowance for receivables | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Total margin lending, brokerage and other receivables, net | $ 12,507 | $ 2,107 | 
| FFIN Brokerage | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Margin lending receivables from related party as a percentage of related party margin lending receivables | 98.00% | 95.00% | 
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- Definition Brokerage And Other Receivables From Related Party As A Percentage Of Related Party Brokerage And Other Receivables No definition available. 
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- Definition Lending Margin Receivable No definition available. 
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- Definition Margin Lending Receivables From Related Party As A Percentage Of Related Party Margin Lending Receivables No definition available. 
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- Definition Related Party Transaction, Brokerage And Other Receivable Due From Related Party 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 Amount due from parties in nontrade transactions, classified as other. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Fair value of the securities pledged as collateral against securities loaned. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Details 
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- Details 
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