Fair Value Measurement - Partnership's Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets
Subtotal	$ 8,316.4	$ 7,962.9
Liabilities
Loans payable of Consolidated Funds	6,809.1	6,298.6
Total Liabilities	6,809.7	6,298.6
Senior secured notes
Liabilities
Loans payable of Consolidated Funds		177.9
Senior and Subordinated Notes
Liabilities
Loans payable of Consolidated Funds		10.0
Revolving Credit Facililty
Liabilities
Loans payable of Consolidated Funds	55.1
Equity securities \| Variable Interest Entity, Primary Beneficiary
Assets
Investments measured at net asset value	441.9	322.0
Foreign currency forward contracts
Liabilities
Foreign currency forward contracts	0.6
Fair Value, Inputs, Level 1, 2 and 3
Assets
Subtotal	7,995.7	7,460.9
Fair Value, Inputs, Level 1, 2 and 3 \| Equity securities
Assets
Investments of consolidated funds	572.0	377.6
Fair Value, Inputs, Level 1, 2 and 3 \| Bonds
Assets
Investments of consolidated funds	465.1	522.5
Fair Value, Inputs, Level 1, 2 and 3 \| Loans
Assets
Investments of consolidated funds	6,431.4	5,862.1
Fair Value, Inputs, Level 1, 2 and 3 \| Other
Assets
Investments of consolidated funds	1.3
Fair Value, Inputs, Level 1, 2 and 3 \| Investments of Consolidated Funds
Assets
Investments of consolidated funds	7,469.8	6,762.2
Fair Value, Inputs, Level 1, 2 and 3 \| Investments in CLOs
Assets
Investments of consolidated funds	378.9	532.6
Fair Value, Inputs, Level 1, 2 and 3 \| Other investments
Assets
Investments of consolidated funds	147.0	166.1
Fair Value, Inputs, Level 1, 2 and 3 \| Investments in CLOs and other, and Partnership and LLC interests
Assets
Investments of consolidated funds	525.9	698.7
Level I
Assets
Subtotal	40.4	38.7
Liabilities
Loans payable of Consolidated Funds	0.0	0.0
Total Liabilities	0.0	0.0
Level I \| Equity securities
Assets
Investments of consolidated funds	0.0	0.0
Level I \| Bonds
Assets
Investments of consolidated funds	0.0	0.0
Level I \| Loans
Assets
Investments of consolidated funds	0.0	0.0
Level I \| Other
Assets
Investments of consolidated funds	0.0
Level I \| Investments of Consolidated Funds
Assets
Investments of consolidated funds	0.0	0.0
Level I \| Investments in CLOs
Assets
Investments of consolidated funds	0.0	0.0
Level I \| Other investments
Assets
Investments of consolidated funds	40.4	38.7
Level I \| Investments in CLOs and other, and Partnership and LLC interests
Assets
Investments of consolidated funds	40.4	38.7
Level I \| Foreign currency forward contracts
Liabilities
Foreign currency forward contracts	0.0
Level II
Assets
Subtotal	22.8	42.8
Liabilities
Loans payable of Consolidated Funds	0.0	0.0
Total Liabilities	0.6	0.0
Level II \| Equity securities
Assets
Investments of consolidated funds	0.0	0.0
Level II \| Bonds
Assets
Investments of consolidated funds	0.0	0.0
Level II \| Loans
Assets
Investments of consolidated funds	0.0	0.0
Level II \| Other
Assets
Investments of consolidated funds	1.3
Level II \| Investments of Consolidated Funds
Assets
Investments of consolidated funds	1.3	0.0
Level II \| Investments in CLOs
Assets
Investments of consolidated funds	0.0	0.0
Level II \| Other investments
Assets
Investments of consolidated funds	21.5	42.8
Level II \| Investments in CLOs and other, and Partnership and LLC interests
Assets
Investments of consolidated funds	21.5	42.8
Level II \| Foreign currency forward contracts
Liabilities
Foreign currency forward contracts	0.6
Level III
Assets
Subtotal	7,932.5	7,379.4
Liabilities
Loans payable of Consolidated Funds	6,809.1	6,298.6
Total Liabilities	6,809.1	6,298.6
Level III \| Equity securities
Assets
Investments of consolidated funds	572.0	377.6
Investments measured at net asset value	55.4	50.4
Level III \| Bonds
Assets
Investments of consolidated funds	465.1	522.5
Level III \| Loans
Assets
Investments of consolidated funds	6,431.4	5,862.1
Level III \| Other
Assets
Investments of consolidated funds	0.0
Level III \| Investments of Consolidated Funds
Assets
Investments of consolidated funds	7,468.5	6,762.2
Subtotal	7,468.5	6,762.2
Level III \| Investments in CLOs
Assets
Investments of consolidated funds	378.9	532.6
Level III \| Other investments
Assets
Investments of consolidated funds	85.1	84.6
Level III \| Investments in CLOs and other, and Partnership and LLC interests
Assets
Investments of consolidated funds	464.0	617.2
Level III \| Foreign currency forward contracts
Liabilities
Foreign currency forward contracts	0.0
Fair Value Measured at NAV
Assets
Investments measured at net asset value	320.7	502.0
Fair Value Measured at NAV \| Investments of Consolidated Funds
Assets
Investments of consolidated funds	$ 312.6	$ 490.9

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