Fair Value Measurement - Changes in Level III Financial Assets Measured at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Equity securities
Realized and unrealized gains (losses), net
Fair value, asset, recurring basis, unobservable input reconciliation, gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Fair value, asset, recurring basis, unobservable input reconciliation, asset, gain (loss), statement of other comprehensive income or comprehensive income	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax
Fair value, asset, recurring basis, still held, unrealized gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Bonds
Realized and unrealized gains (losses), net
Fair value, asset, recurring basis, unobservable input reconciliation, gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Fair value, asset, recurring basis, unobservable input reconciliation, asset, gain (loss), statement of other comprehensive income or comprehensive income	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax
Fair value, asset, recurring basis, still held, unrealized gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Loans
Realized and unrealized gains (losses), net
Fair value, asset, recurring basis, unobservable input reconciliation, gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Fair value, asset, recurring basis, unobservable input reconciliation, asset, gain (loss), statement of other comprehensive income or comprehensive income	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax
Fair value, asset, recurring basis, still held, unrealized gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Investments in CLOs
Realized and unrealized gains (losses), net
Fair value, asset, recurring basis, unobservable input reconciliation, gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Fair value, asset, recurring basis, unobservable input reconciliation, asset, gain (loss), statement of other comprehensive income or comprehensive income	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax
Fair value, asset, recurring basis, still held, unrealized gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Deconsolidation of funds		$ 0.0	$ 0.0
Realized and unrealized gains (losses), net
Fair value, asset, recurring basis, unobservable input reconciliation, gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Fair value, asset, recurring basis, unobservable input reconciliation, asset, gain (loss), statement of other comprehensive income or comprehensive income	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax	Other Comprehensive Income (Loss), Net of Tax
Fair value, asset, recurring basis, still held, unrealized gain (loss), statement of income or comprehensive income	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds	Net investment income (loss) of Consolidated Funds
Level III
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 7,566.6	$ 7,131.3	$ 7,379.4	$ 6,983.9
Deconsolidation of funds		(372.6)		(372.6)
Purchases	2,396.8	1,295.8	3,866.4	1,568.3
Sales and distributions	(911.7)	(360.2)	(1,745.0)	(585.7)
Settlements	(520.7)	(181.4)	(985.4)	(287.1)
Realized and unrealized gains (losses), net
Included in earnings	28.4	(23.6)	132.5	120.0
Included in other comprehensive income	(22.7)	24.7	(111.2)	87.2
Balance, end of period	8,536.7	7,514.0	8,536.7	7,514.0
Changes in unrealized gains (losses) included in earnings related to financial assets still held at the reporting date	28.7	(16.0)	123.9	113.2
Changes in unrealized gains (losses) included in other comprehensive income related to financial assets still held at the reporting date	(21.6)	27.1	(88.2)	83.3
Level III | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	387.3	435.5	377.6	430.6
Deconsolidation of funds		(0.4)		(0.4)
Purchases	38.2	53.1	63.0	58.5
Sales and distributions	(4.0)	0.0	(10.1)	0.0
Settlements	0.0	0.0	0.0	0.0
Realized and unrealized gains (losses), net
Included in earnings	(1.5)	(0.6)	(10.5)	(1.1)
Included in other comprehensive income	0.0	0.0	0.0	0.0
Balance, end of period	420.0	487.6	420.0	487.6
Changes in unrealized gains (losses) included in earnings related to financial assets still held at the reporting date	(4.6)	(0.6)	(13.0)	(1.0)
Changes in unrealized gains (losses) included in other comprehensive income related to financial assets still held at the reporting date	0.0	0.0	0.0	0.0
Level III | Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	500.4	593.2	522.5	594.9
Deconsolidation of funds		0.0		0.0
Purchases	71.7	41.8	118.1	71.6
Sales and distributions	(70.0)	(81.3)	(142.8)	(128.3)
Settlements	0.0	(4.1)	0.0	(8.2)
Realized and unrealized gains (losses), net
Included in earnings	(9.7)	(3.3)	5.9	8.1
Included in other comprehensive income	(2.9)	2.1	(14.2)	10.3
Balance, end of period	489.5	548.4	489.5	548.4
Changes in unrealized gains (losses) included in earnings related to financial assets still held at the reporting date	(6.5)	(4.5)	8.6	2.2
Changes in unrealized gains (losses) included in other comprehensive income related to financial assets still held at the reporting date	(2.6)	2.2	(11.2)	9.0
Level III | Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	6,064.9	5,481.7	5,862.1	5,352.9
Deconsolidation of funds		(372.2)		(372.2)
Purchases	2,279.7	1,200.9	3,677.1	1,438.2
Sales and distributions	(801.2)	(265.3)	(1,530.7)	(435.0)
Settlements	(520.7)	(177.3)	(985.4)	(278.9)
Realized and unrealized gains (losses), net
Included in earnings	20.7	(22.7)	93.5	93.3
Included in other comprehensive income	(19.4)	13.3	(92.6)	60.1
Balance, end of period	7,024.0	5,858.4	7,024.0	5,858.4
Changes in unrealized gains (losses) included in earnings related to financial assets still held at the reporting date	20.9	(13.1)	85.6	94.0
Changes in unrealized gains (losses) included in other comprehensive income related to financial assets still held at the reporting date	(18.6)	15.6	(72.6)	57.5
Level III | Investments in CLOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	520.8	544.8	532.6	526.1
Deconsolidation of funds		0.0		0.0
Purchases	0.0	0.0	1.0	0.0
Sales and distributions	(36.5)	(12.8)	(60.5)	(20.7)
Settlements	0.0	0.0	0.0	0.0
Realized and unrealized gains (losses), net
Included in earnings	10.7	(3.2)	25.9	15.9
Included in other comprehensive income	(0.4)	9.3	(4.4)	16.8
Balance, end of period	494.6	538.1	494.6	538.1
Changes in unrealized gains (losses) included in earnings related to financial assets still held at the reporting date	10.7	(3.2)	25.9	15.9
Changes in unrealized gains (losses) included in other comprehensive income related to financial assets still held at the reporting date	(0.4)	9.3	(4.4)	16.8
Level III | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	93.2	76.1	84.6	79.4
Purchases	7.2	0.0	7.2	0.0
Sales and distributions	0.0	(0.8)	(0.9)	(1.7)
Settlements	0.0	0.0	0.0	0.0
Realized and unrealized gains (losses), net
Included in earnings	8.2	6.2	17.7	3.8
Included in other comprehensive income	0.0	0.0	0.0	0.0
Balance, end of period	108.6	81.5	108.6	81.5
Changes in unrealized gains (losses) included in earnings related to financial assets still held at the reporting date	8.2	5.4	16.8	2.1
Changes in unrealized gains (losses) included in other comprehensive income related to financial assets still held at the reporting date	$ 0.0	$ 0.0	$ 0.0	$ 0.0