NET GAIN ON TRADING SECURITIES - Narrative (Details) - USD ($) $ in Thousands  | 
12 Months Ended | ||
|---|---|---|---|
Mar. 31, 2023  | 
Mar. 31, 2022  | 
Mar. 31, 2021  | 
|
| Debt Securities, Available-for-Sale [Line Items] | |||
| Equity securities FVNI portfolio shares SPBX | $ 478 | $ 18,408 | $ 11,259 | 
| Number of equity shares exchanged (in shares) | 7,500,000 | ||
| Debt securities, trading, realized gain (loss) | $ 36,226 | (206,239) | (20,135) | 
| Debt Securities, Trading, Unrealized Gain (Loss) | (107,310) | 50,987 | (8,672) | 
| Net gain on trading securities | 71,084 | $ 155,252 | $ 28,807 | 
| SBPX Shares | |||
| Debt Securities, Available-for-Sale [Line Items] | |||
| Debt securities, trading, realized gain (loss) | 73,384 | ||
| Debt Securities, Trading, Unrealized Gain (Loss) | $ 50,785 | ||
| X | ||||||||||
- Definition Equity Securities FVNI Portfolio Shares SPBX No definition available. 
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- Definition Number Of Equity Shares Exchanged No definition available. 
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- Definition Amount of unrealized and realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading). Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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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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- Details 
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