CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Consolidated revenue	$ 516.4	$ 525.2	$ 1,516.6	$ 1,555.2
Consolidated expenses:
Compensation and related expenses	220.8	211.8	676.5	663.0
Selling, general and administrative	97.0	91.1	278.1	273.4
Intangible amortization and impairments	7.3	12.5	21.8	37.5
Interest expense	34.7	31.1	98.1	92.4
Depreciation and other amortization	3.3	3.0	9.4	10.0
Other expenses (net)	11.6	7.9	31.5	36.2
Total consolidated expenses	374.7	357.4	1,115.4	1,112.5
Equity method income (net)	52.6	39.8	188.3	154.3
Affiliate Transaction gain	0.0	133.1	0.0	133.1
Investment and other income	22.8	23.0	60.0	87.2
Income before income taxes	217.1	363.7	649.5	817.3
Income tax expense	31.3	77.7	130.0	155.4
Net income	185.8	286.0	519.5	661.9
Net income (non-controlling interests)	(62.2)	(69.0)	(170.0)	(185.1)
Net income (controlling interest)	$ 123.6	$ 217.0	$ 349.5	$ 476.8
Average shares outstanding (basic) (in shares)	30.1	34.9	31.4	35.6
Average shares outstanding (diluted) (in shares)	35.0	43.4	35.2	42.9
Earnings per share (basic) (in dollars per share)	$ 4.11	$ 6.22	$ 11.11	$ 13.41
Earnings per share (diluted) (in dollars per share)	$ 3.78	$ 5.48	$ 10.25	$ 12.28