RESTRICTED CASH - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 1,473,196	$ 1,246,312
Brokerage customers’ cash
Cash and Cash Equivalents [Line Items]
Restricted cash	1,303,828	1,095,026
Single non-related prime broker \| Brokerage customers’ cash
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 1,169,474	$ 684,476

Amount of cash restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.