INVESTMENTS - Yields at Amortized Cost and Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2024		Dec. 31, 2023
Schedule of Investments [Line Items]
Amortized Cost	$ 26,374.0	[1]	$ 22,667.6	[2]
Fair Value	$ 26,719.9	[1]	$ 22,873.7	[2]
Subordinated loan
Schedule of Investments [Line Items]
Yield on investment, at cost	0.00%		12.00%
Yield on investment, at fair value	0.00%		12.00%
Amortized Cost	$ 0.0		$ 62.0
Fair Value	$ 0.0		$ 62.0
Equity
Schedule of Investments [Line Items]
Yield on investment, at cost	16.70%		15.10%
Yield on investment, at fair value	14.80%		13.30%
Amortized Cost	$ 1,701.0		$ 1,701.0
Fair Value	$ 1,915.0		$ 1,925.0
Subordinated certificates of the SDLP
Schedule of Investments [Line Items]
Yield on investment, at cost	12.40%		13.60%
Yield on investment, at fair value	13.20%		13.90%
Amortized Cost	$ 1,263.0		$ 1,316.0
Fair Value	$ 1,192.0		$ 1,288.0

[1] As of December 31, 2024, the estimated net unrealized gain for federal tax purposes was $0.2 billion based on a tax cost basis of $26.5 billion. As of December 31, 2024, the estimated aggregate gross unrealized gain for federal income tax purposes was $1.7 billion and the estimated aggregate gross unrealized loss for federal income tax purposes was $1.5 billion.     

[2] As of December 31, 2023, the estimated net unrealized loss for federal tax purposes was $0.4 billion based on a tax cost basis of $22.5 billion. As of December 31, 2023, the estimated aggregate gross unrealized loss for federal income tax purposes was $1.7 billion and the estimated aggregate gross unrealized gain for federal income tax purposes was $1.3 billion.