Supplemental Financial Information - Financial Position (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents	$ 1,440.3	$ 1,360.7	$ 2,469.5
Cash and cash equivalents held at Consolidated Funds	346.0	209.0	147.8
Restricted cash	1.8	0.8	5.6
Corporate treasury investments	0.0	20.0
Investments, including performance allocations of $6,169.9	9,955.3	10,767.9
Investments of Consolidated Funds	7,253.1	6,894.4
Due from affiliates and other receivables, net	691.6	579.4
Due from affiliates and other receivables of Consolidated Funds, net	141.0	101.9
Fixed assets, net	161.5	139.9
Lease right-of-use assets, net	332.2	337.0
Deposits and other	70.6	78.4
Intangible assets, net	766.1	897.8
Deferred tax assets	16.5	15.8
Total assets	21,176.0	21,403.0	21,250.4
Liabilities and equity
Debt obligations	2,281.0	2,271.7
Loans payable of Consolidated Funds	6,486.5	5,905.2
Accounts payable, accrued expenses and other liabilities	333.8	369.2
Accrued compensation and benefits	4,922.2	4,320.9
Other liabilities	275.9	362.5
Deferred revenue	140.3	126.4
Deferred tax liabilities	45.3	402.7
Other liabilities of Consolidated Funds	374.4	279.3
Lease liabilities	488.1	502.9
Accrued giveback obligations	44.0	40.9
Total liabilities	15,391.5	14,581.7
Common stock	3.6	3.6
Additional paid-in capital	3,403.0	3,138.5
Retained earnings	2,082.1	3,401.1
Accumulated other comprehensive loss	(297.3)	(322.2)
Non-controlling interests in consolidated entities	593.1	600.3
Total equity	5,784.5	6,821.3	5,706.2	$ 2,930.2
Total liabilities and equity	21,176.0	21,403.0
Accrued performance allocations	6,169.9	7,117.7
Consolidated Operating Entities
Assets
Cash and cash equivalents	1,440.3	1,360.7	2,469.5
Cash and cash equivalents held at Consolidated Funds	346.0	209.0	147.8
Restricted cash	1.8	0.8	5.6
Consolidated Entities | Consolidated Operating Entities
Assets
Cash and cash equivalents	1,440.3	1,360.7
Cash and cash equivalents held at Consolidated Funds	0.0	0.0
Restricted cash	1.8	0.8
Corporate treasury investments		20.0
Investments, including performance allocations of $6,169.9	10,104.5	10,989.9
Investments of Consolidated Funds	0.0	0.0
Due from affiliates and other receivables, net	1,009.2	960.5
Due from affiliates and other receivables of Consolidated Funds, net	0.0	0.0
Fixed assets, net	161.5	139.9
Lease right-of-use assets, net	332.2	337.0
Deposits and other	66.0	70.4
Intangible assets, net	766.1	897.8
Deferred tax assets	16.5	15.8
Total assets	13,898.1	14,792.8
Liabilities and equity
Debt obligations	2,281.0	2,271.7
Loans payable of Consolidated Funds	0.0	0.0
Accounts payable, accrued expenses and other liabilities	333.8	369.2
Accrued compensation and benefits	4,922.2	4,320.9
Other liabilities	269.6	346.1
Deferred revenue	140.3	126.4
Deferred tax liabilities	45.3	402.7
Other liabilities of Consolidated Funds	0.0	0.0
Lease liabilities	488.1	502.9
Accrued giveback obligations	44.0	40.9
Total liabilities	8,524.3	8,380.8
Common stock	3.6	3.6
Additional paid-in capital	3,403.0	3,138.5
Retained earnings	2,082.1	3,401.1
Accumulated other comprehensive loss	(292.7)	(319.5)
Non-controlling interests in consolidated entities	177.8	188.3
Total equity	5,373.8	6,412.0
Total liabilities and equity	13,898.1	14,792.8
Consolidated Entities | Consolidated Funds
Assets
Cash and cash equivalents	0.0	0.0
Cash and cash equivalents held at Consolidated Funds	346.0	209.0
Restricted cash	0.0	0.0
Corporate treasury investments		0.0
Investments, including performance allocations of $6,169.9	0.0	0.0
Investments of Consolidated Funds	7,313.9	6,894.4
Due from affiliates and other receivables, net	0.0	0.0
Due from affiliates and other receivables of Consolidated Funds, net	141.0	101.9
Fixed assets, net	0.0	0.0
Lease right-of-use assets, net	0.0	0.0
Deposits and other	4.6	8.0
Intangible assets, net	0.0	0.0
Deferred tax assets	0.0	0.0
Total assets	7,805.5	7,213.3	$ 6,948.0
Liabilities and equity
Debt obligations	0.0	0.0
Loans payable of Consolidated Funds	6,796.4	6,279.7
Accounts payable, accrued expenses and other liabilities	0.0	0.0
Accrued compensation and benefits	0.0	0.0
Other liabilities	6.3	16.5
Deferred revenue	0.0	0.0
Deferred tax liabilities	0.0	0.0
Other liabilities of Consolidated Funds	374.4	279.7
Lease liabilities	0.0	0.0
Accrued giveback obligations	0.0	0.0
Total liabilities	7,177.1	6,575.9
Common stock	0.0	0.0
Additional paid-in capital	223.8	238.7
Retained earnings	0.0	0.0
Accumulated other comprehensive loss	(10.7)	(13.3)
Non-controlling interests in consolidated entities	415.3	412.0
Total equity	628.4	637.4
Total liabilities and equity	7,805.5	7,213.3
Eliminations
Assets
Cash and cash equivalents	0.0	0.0
Cash and cash equivalents held at Consolidated Funds	0.0	0.0
Restricted cash	0.0	0.0
Corporate treasury investments		0.0
Investments, including performance allocations of $6,169.9	(149.2)	(222.0)
Investments of Consolidated Funds	(60.8)	0.0
Due from affiliates and other receivables, net	(317.6)	(381.1)
Due from affiliates and other receivables of Consolidated Funds, net	0.0	0.0
Fixed assets, net	0.0	0.0
Lease right-of-use assets, net	0.0	0.0
Deposits and other	0.0	0.0
Intangible assets, net	0.0	0.0
Deferred tax assets	0.0	0.0
Total assets	(527.6)	(603.1)
Liabilities and equity
Debt obligations	0.0	0.0
Loans payable of Consolidated Funds	(309.9)	(374.5)
Accounts payable, accrued expenses and other liabilities	0.0	0.0
Accrued compensation and benefits	0.0	0.0
Other liabilities	0.0	(0.1)
Deferred revenue	0.0	0.0
Deferred tax liabilities	0.0	0.0
Other liabilities of Consolidated Funds	0.0	(0.4)
Lease liabilities	0.0	0.0
Accrued giveback obligations	0.0	0.0
Total liabilities	(309.9)	(375.0)
Common stock	0.0	0.0
Additional paid-in capital	(223.8)	(238.7)
Retained earnings	0.0	0.0
Accumulated other comprehensive loss	6.1	10.6
Non-controlling interests in consolidated entities	0.0	0.0
Total equity	(217.7)	(228.1)
Total liabilities and equity	$ (527.6)	$ (603.1)