v3.26.3
FAIR VALUE OF ASSETS AND LIABILITIES - Tri-Level Hierarchy, Carrying Value (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Equity investments:    
Equity investments $ 303.8 $ 414.4
Total 708.2 900.1
Liabilities:    
Total (20.5)  
Equity method investments 1,049.7 937.1
Other investments 12.6 29.6
Money market funds    
Cash equivalents:    
Money market funds 404.4 477.9
Total return swap related to deferred compensation plans    
Equity investments:    
Total return swap related to deferred compensation plans   7.8
Liabilities:    
Total return swap related to deferred compensation plans (20.5)  
Seed capital    
Equity investments:    
Equity investments 132.0 286.2
Investments related to deferred compensation plans    
Equity investments:    
Equity investments 135.1 128.2
Other equity securities    
Equity investments:    
Equity investments 36.7  
Quoted Prices in Active Markets for Identical Assets (Level 1)    
Equity investments:    
Total 708.2 745.9
Liabilities:    
Total 0.0  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds    
Cash equivalents:    
Money market funds 404.4 477.9
Quoted Prices in Active Markets for Identical Assets (Level 1) | Total return swap related to deferred compensation plans    
Equity investments:    
Total return swap related to deferred compensation plans   0.0
Liabilities:    
Total return swap related to deferred compensation plans 0.0  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Seed capital    
Equity investments:    
Equity investments 132.0 139.8
Quoted Prices in Active Markets for Identical Assets (Level 1) | Investments related to deferred compensation plans    
Equity investments:    
Equity investments 135.1 128.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other equity securities    
Equity investments:    
Equity investments 36.7  
Significant Other Observable Inputs (Level 2)    
Equity investments:    
Total 0.0 154.2
Liabilities:    
Total (20.5)  
Significant Other Observable Inputs (Level 2) | Money market funds    
Cash equivalents:    
Money market funds 0.0 0.0
Significant Other Observable Inputs (Level 2) | Total return swap related to deferred compensation plans    
Equity investments:    
Total return swap related to deferred compensation plans   7.8
Liabilities:    
Total return swap related to deferred compensation plans (20.5)  
Significant Other Observable Inputs (Level 2) | Seed capital    
Equity investments:    
Equity investments 0.0 146.4
Significant Other Observable Inputs (Level 2) | Investments related to deferred compensation plans    
Equity investments:    
Equity investments 0.0 0.0
Significant Other Observable Inputs (Level 2) | Other equity securities    
Equity investments:    
Equity investments 0.0  
Significant Unobservable Inputs (Level 3)    
Equity investments:    
Total 0.0 0.0
Liabilities:    
Total 0.0  
Significant Unobservable Inputs (Level 3) | Money market funds    
Cash equivalents:    
Money market funds 0.0 0.0
Significant Unobservable Inputs (Level 3) | Total return swap related to deferred compensation plans    
Equity investments:    
Total return swap related to deferred compensation plans   0.0
Liabilities:    
Total return swap related to deferred compensation plans 0.0  
Significant Unobservable Inputs (Level 3) | Seed capital    
Equity investments:    
Equity investments 0.0 0.0
Significant Unobservable Inputs (Level 3) | Investments related to deferred compensation plans    
Equity investments:    
Equity investments 0.0 $ 0.0
Significant Unobservable Inputs (Level 3) | Other equity securities    
Equity investments:    
Equity investments $ 0.0