Borrowings - Outstanding Loans Payable of Consolidated Funds (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2025	Dec. 31, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of liabilities	$ 8,213.1	$ 6,809.7
Revolving credit facilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	61.9	55.1
Fair Value	$ 61.9	$ 55.1
Weighted Average Interest Rate	6.81%	7.01%
Weighted Average Remaining Maturity in Years	3 years 8 months 23 days	4 years 6 months 10 days
Loans Payable of Consolidated Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	$ 9,322.2	$ 7,017.8
Fair Value	9,199.5	6,864.2
Senior secured notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	8,889.2	6,732.8
Fair Value	$ 8,825.5	$ 6,598.8
Weighted Average Interest Rate	5.44%	5.72%
Weighted Average Remaining Maturity in Years	10 years 8 months 26 days	9 years 2 months 4 days
Fair value of liabilities	$ 928.9
Subordinated notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Borrowing Outstanding	371.1	$ 229.9
Fair Value	$ 312.1	$ 210.3
Weighted Average Remaining Maturity in Years	9 years 9 months 25 days	9 years 1 month 24 days