Borrowings - Outstanding Loans Payable of Consolidated Funds (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowings at amortized cost	$ 10,160.4	$ 9,427.5
Revolving credit facilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	51.0	63.0
Fair Value	$ 51.0	$ 63.0
Weighted Average Interest Rate	6.77%	6.68%
Weighted Average Remaining Maturity in Years	3 years 3 months 10 days	3 years 5 months 12 days
Loans Payable of Consolidated Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	$ 11,308.2	$ 10,567.4
Fair Value	11,148.7	10,426.0
Senior secured notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	10,875.4	9,994.8
Fair Value	$ 10,761.3	$ 9,972.1
Weighted Average Interest Rate	5.01%	5.09%
Weighted Average Remaining Maturity in Years	11 years 2 months 15 days	11 years 2 months 4 days
Borrowings at amortized cost	$ 940.9	$ 939.9
Subordinated notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	381.8	509.6
Fair Value	$ 336.4	$ 390.9
Weighted Average Remaining Maturity in Years	10 years 29 days	9 years 7 months 24 days