COLLATERALIZED ARRANGEMENTS AND FINANCING - Crypto Assets Held as Collateral and Obligation to Return (Details) $ in Thousands	Sep. 30, 2026 USD ($) unit	Dec. 31, 2025 USD ($) unit
Crypto Asset, Holding [Line Items]
Crypto assets held as collateral	$ 1,299,500	$ 822,827
Total recognized lending collateral	1,009,297	799,484
Asset Pledged as Collateral without Right
Crypto Asset, Holding [Line Items]
Total customer collateral not recognized as collateral	3,284,562	1,863,441
Fiat and Payment Stablecoins
Crypto Asset, Holding [Line Items]
Crypto assets held as collateral	11,740	4,056
Fiat and Payment Stablecoins \| Asset Pledged as Collateral without Right
Crypto Asset, Holding [Line Items]
Total customer collateral not recognized as collateral	480,450	303,983
Crypto Assets
Crypto Asset, Holding [Line Items]
Cost Basis	870,527	861,078
Crypto assets held as collateral	$ 997,557	$ 795,428
Crypto Assets \| Bitcoin
Crypto Asset, Holding [Line Items]
Units \| unit	11,018	8,479
Cost Basis	$ 803,951	$ 810,055
Crypto assets held as collateral	$ 920,649	$ 747,697
Crypto Assets \| Ethereum
Crypto Asset, Holding [Line Items]
Units \| unit	24,965	16,041
Cost Basis	$ 57,962	$ 51,023
Crypto assets held as collateral	67,005	$ 47,731
Crypto Assets \| Other crypto assets
Crypto Asset, Holding [Line Items]
Units \| unit		0
Cost Basis	8,614	$ 0
Crypto assets held as collateral	9,903	0
Crypto Assets \| Asset Pledged as Collateral without Right
Crypto Asset, Holding [Line Items]
Total customer collateral not recognized as collateral	$ 2,804,112	$ 1,559,458