CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Statement [Abstract]
Consolidated revenue	$ 2,074.4	$ 2,040.9	$ 2,057.8
Consolidated expenses:
Compensation and related expenses	1,019.8	915.3	907.5
Selling, general and administrative	408.6	376.5	358.2
Intangible amortization and impairments	160.3	29.0	48.3
Interest expense	136.5	133.3	123.8
Depreciation and other amortization	10.4	13.4	13.0
Other expenses (net)	69.8	40.3	45.8
Total consolidated expenses	1,805.4	1,507.8	1,496.6
Equity method income (net)	462.9	312.7	280.0
Affiliate transaction gains	371.3	0.0	133.1
Investment and other income	83.1	77.4	117.1
Income before income taxes	1,186.3	923.2	1,091.4
Income tax expense	282.3	182.6	185.3
Net income	904.0	740.6	906.1
Net income (non-controlling interests)	(187.4)	(229.0)	(233.2)
Net income (controlling interest)	$ 716.6	$ 511.6	$ 672.9
Average shares outstanding (basic) (in shares)	28.5	31.1	35.1
Average shares outstanding (diluted) (in shares)	33.0	36.1	42.2
Earnings per share (basic) (in dollars per share)	$ 25.18	$ 16.45	$ 19.18
Earnings per share (diluted) (in dollars per share)	$ 22.74	$ 15.13	$ 17.42