INVESTMENTS - Yields at Amortized Cost and Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Schedule of Investments [Line Items]
Amortized Cost	$ 29,647.5	$ 29,249.9	[1]
Fair Value	$ 29,499.3	$ 29,484.8	[1]
Subordinated loan
Schedule of Investments [Line Items]
Yield on investment, at cost	10.30%	10.30%
Yield on investment, at fair value	10.30%	10.30%
Amortized Cost	$ 762.0	$ 531.0
Fair Value	$ 762.0	$ 531.0
Equity
Schedule of Investments [Line Items]
Yield on investment, at cost	17.60%	17.20%
Yield on investment, at fair value	15.80%	15.30%
Amortized Cost	$ 1,700.0	$ 1,700.0
Fair Value	$ 1,899.0	$ 1,903.0
Subordinated certificates of the SDLP
Schedule of Investments [Line Items]
Yield on investment, at cost	13.20%	13.20%
Yield on investment, at fair value	13.00%	13.00%
Amortized Cost	$ 1,146.0	$ 1,103.0
Fair Value	$ 1,159.0	$ 1,117.0

[1] As of December 31, 2025, the estimated net unrealized gain for federal tax purposes was approximately $300 million based on a tax cost basis of $29.2 billion. As of December 31, 2025, the estimated aggregate gross unrealized gain for federal income tax purposes was approximately $1.3 billion and the estimated aggregate gross unrealized loss for federal income tax purposes was approximately $1.0 billion.