INCOME AND EXCISE TAXES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025		Dec. 31, 2024		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Owned, Federal Income Tax Note [Line Items]
Capital loss carryforward	$ 278.0
Capital loss carryforwards subject to limitations	92.0
Carry forward of excess distributable earnings	988.0		$ 878.0		$ 631.0
Excise tax expense	37.0		35.0		23.0
Refund request for overpayment of excise taxes	2.0		1.0
Tax cost basis	29,200.0		26,500.0
Aggregate gross unrealized gain for federal tax purposes	1,300.0		1,700.0
Unrealized losses	1,000.0		1,500.0
Amortized cost of investments	29,300.0
Amortized cost of investments	29,249.9	[1]	26,374.0	[2]
Tax reclassification of stockholders' equity, increase (decreased)	0.0		0.0		0.0
Total stockholders’ equity	14,318.0		13,355.0		11,201.0	$ 9,555.0	$ 8,868.0	$ 7,176.0	$ 7,467.0	$ 7,300.0	$ 7,098.0	$ 5,165.0
Income tax expense, including excise taxes	43.0		40.0		28.0
Subsidiaries
Investments, Owned, Federal Income Tax Note [Line Items]
Income tax expense, including excise taxes	121.0		38.0		(3.0)
Capital in Excess of Par Value
Investments, Owned, Federal Income Tax Note [Line Items]
Tax reclassification of stockholders' equity, increase (decreased)	(158.0)		(87.0)		(20.0)
Total stockholders’ equity	13,359.0		12,502.0		10,738.0	9,556.0
Accumulated Undistributed (Overdistributed) Earnings
Investments, Owned, Federal Income Tax Note [Line Items]
Tax reclassification of stockholders' equity, increase (decreased)	158.0		87.0		20.0
Total stockholders’ equity	958.0		852.0		$ 462.0	$ (2.0)
Retained Earnings, Accumulated Undistributed Net Investment Income
Investments, Owned, Federal Income Tax Note [Line Items]
Total stockholders’ equity	1,077.0		921.0
Retained Earnings, Accumulated Net Realized Losses
Investments, Owned, Federal Income Tax Note [Line Items]
Total stockholders’ equity	(270.0)		(316.0)
Retained Earnings, Accumulated Net Unrealized Gains
Investments, Owned, Federal Income Tax Note [Line Items]
Total stockholders’ equity	$ 151.0		$ 247.0

[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.

[2] 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.