Investments - Schedule of Investments as a Percentage of Investments of Consolidated Funds (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Investments of Consolidated Funds	$ 7,253.1	$ 6,894.4
Percentage of investments in Consolidated Funds	100.00%	100.00%
Minimum percent of aggregate assets for individual investments with fair value	5.00%
Assets of the CLOs - Equity
Schedule of Investments [Line Items]
Assets of CLOs	$ 1.3	$ 2.1
Percentage of assets of the CLOs	0.02%	0.03%
United States
Schedule of Investments [Line Items]
Investments of Consolidated Funds	$ 4,086.4	$ 3,743.3
Percentage of investments in Consolidated Funds	56.34%	54.29%
United States | Equity securities
Schedule of Investments [Line Items]
Equity securities	$ 374.3	$ 427.3
Percentage of equity securities	5.16%	6.20%
United States | Partnership and LLC interests
Schedule of Investments [Line Items]
Fund investments	$ 490.9	$ 515.9
Percentage of fund investments	6.77%	7.48%
United States | Loans
Schedule of Investments [Line Items]
Loans	$ 38.7	$ 23.4
Loans percentage	0.53%	0.34%
United States | Assets of the CLOs - Bonds
Schedule of Investments [Line Items]
Assets of CLOs	$ 80.5	$ 57.5
Percentage of assets of the CLOs	1.11%	0.83%
United States | Assets of the CLOs - Equity
Schedule of Investments [Line Items]
Assets of CLOs	$ 2.0	$ 1.3
Percentage of assets of the CLOs	0.03%	0.02%
United States | Assets of the CLOs - Loans
Schedule of Investments [Line Items]
Assets of CLOs	$ 3,100.0	$ 2,717.9
Percentage of assets of the CLOs	42.74%	39.42%
United States | Total assets of the CLOs
Schedule of Investments [Line Items]
Assets of CLOs	$ 3,182.5	$ 2,776.7
Percentage of assets of the CLOs	43.88%	40.27%
Europe
Schedule of Investments [Line Items]
Investments of Consolidated Funds	$ 3,091.8	$ 3,062.8
Percentage of investments in Consolidated Funds	42.63%	44.43%
Europe | Assets of the CLOs - Bonds
Schedule of Investments [Line Items]
Assets of CLOs	$ 437.9	$ 533.5
Percentage of assets of the CLOs	6.04%	7.74%
Europe | Assets of the CLOs - Loans
Schedule of Investments [Line Items]
Assets of CLOs	$ 2,652.6	$ 2,527.2
Percentage of assets of the CLOs	36.57%	36.66%
Europe | Total assets of the CLOs
Schedule of Investments [Line Items]
Assets of CLOs	$ 3,091.8	$ 3,062.8
Percentage of assets of the CLOs	42.63%	44.43%
Global
Schedule of Investments [Line Items]
Investments of Consolidated Funds	$ 74.9	$ 88.3
Percentage of investments in Consolidated Funds	1.03%	1.28%
Global | Assets of the CLOs - Bonds
Schedule of Investments [Line Items]
Assets of CLOs	$ 4.1	$ 3.9
Percentage of assets of the CLOs	0.06%	0.06%
Global | Assets of the CLOs - Loans
Schedule of Investments [Line Items]
Assets of CLOs	$ 70.8	$ 84.4
Percentage of assets of the CLOs	0.97%	1.22%
Global | Total assets of the CLOs
Schedule of Investments [Line Items]
Assets of CLOs	$ 74.9	$ 88.3
Percentage of assets of the CLOs	1.03%	1.28%
Infrastructure | United States | Equity securities
Schedule of Investments [Line Items]
Equity securities	$ 366.5	$ 413.4
Percentage of equity securities	5.05%	6.00%
Aerospace & Defense | United States | Loans
Schedule of Investments [Line Items]
Loans	$ 10.1	$ 10.9
Loans percentage	0.14%	0.16%
Collateralized Debt Obligation | United States | Loans
Schedule of Investments [Line Items]
Loans	$ 13.0	$ 11.6
Loans percentage	0.18%	0.17%
Environmental Industries | United States | Loans
Schedule of Investments [Line Items]
Loans	$ 0.9	$ 0.9
Loans percentage	0.01%	0.01%
Education | United States | Loans
Schedule of Investments [Line Items]
Loans	$ 14.7	$ 0.0
Loans percentage	0.20%	0.00%
Other | United States | Equity securities
Schedule of Investments [Line Items]
Equity securities	$ 7.8	$ 13.9
Percentage of equity securities	0.11%	0.20%