DERIVATIVE INSTRUMENTS - Summary of Certain Characteristics of Futures Derivatives (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Futures contracts
Derivative [Line Items]
Weighted Average Years to Maturity	9 years 25 days	7 years 1 month 9 days
Futures contracts | Notional - Long Positions
Derivative [Line Items]
Current notional	$ 1,783,700	$ 8,472,100
Futures contracts | Notional - Short Positions
Derivative [Line Items]
Current notional	$ 15,527,500	$ 9,840,500
U.S. Treasury futures - 2 year
Derivative [Line Items]
Maturity period	2 years	2 years
Weighted Average Years to Maturity	2 years	1 year 11 months 23 days
U.S. Treasury futures - 2 year | Notional - Long Positions
Derivative [Line Items]
Current notional	$ 0	$ 6,511,600
U.S. Treasury futures - 2 year | Notional - Short Positions
Derivative [Line Items]
Current notional	$ 3,658,000	$ 0
U.S. Treasury futures - 5 year
Derivative [Line Items]
Maturity period	5 years	5 years
Weighted Average Years to Maturity	4 years 4 months 24 days	4 years 4 months 24 days
U.S. Treasury futures - 5 year | Notional - Long Positions
Derivative [Line Items]
Current notional	$ 1,783,700	$ 1,960,500
U.S. Treasury futures - 5 year | Notional - Short Positions
Derivative [Line Items]
Current notional	$ 0	$ 0
U.S. Treasury futures - 10 year and greater
Derivative [Line Items]
Maturity period	10 years	10 years
Weighted Average Years to Maturity	11 years 11 months 12 days	11 years 18 days
U.S. Treasury futures - 10 year and greater | Notional - Long Positions
Derivative [Line Items]
Current notional	$ 0	$ 0
U.S. Treasury futures - 10 year and greater | Notional - Short Positions
Derivative [Line Items]
Current notional	$ 11,869,500	$ 9,840,500