v3.25.1
Investments - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Millions
Mar. 31, 2025
Dec. 31, 2024
Schedule of Investments [Line Items]    
Deferred compensation liabilities [1] $ (9.0) $ (11.5)
Total 3,872.3 2,670.7
Money Market Funds [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [2] 3,839.8 2,637.5
Seed Capital Investments    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 23.0 23.1
Marketable Equity Securities [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 18.5 21.6
Quoted prices in Active Markets for Identical Assets (Level 1) [Member]    
Schedule of Investments [Line Items]    
Deferred compensation liabilities [1] (9.0) (11.5)
Total 3,872.3 2,670.7
Quoted prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [2] 3,839.8 2,637.5
Quoted prices in Active Markets for Identical Assets (Level 1) [Member] | Seed Capital Investments    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 23.0 23.1
Quoted prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable Equity Securities [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 18.5 21.6
Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Investments [Line Items]    
Deferred compensation liabilities [1] 0.0 0.0
Total 0.0 0.0
Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [2] 0.0 0.0
Significant Other Observable Inputs (Level 2) [Member] | Seed Capital Investments    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 0.0 0.0
Significant Other Observable Inputs (Level 2) [Member] | Marketable Equity Securities [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 0.0 0.0
Significant Unobservable Inputs (Level 3) [Member]    
Schedule of Investments [Line Items]    
Deferred compensation liabilities [1] 0.0 0.0
Total   0.0
Significant Unobservable Inputs (Level 3) [Member] | Money Market Funds [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [2] 0.0 0.0
Significant Unobservable Inputs (Level 3) [Member] | Seed Capital Investments    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 0.0 0.0
Significant Unobservable Inputs (Level 3) [Member] | Marketable Equity Securities [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] $ 0.0 $ 0.0
[1] Included in Other long-term liabilities on the Condensed Consolidated Balance Sheet
[2] As of March 31, 2025, included $173.3 million of cash and cash equivalents, $1.0 million of restricted cash and $3,665.5 million of funds receivable and funds held on behalf of clients on the Condensed Consolidated Balance Sheet. As of December 31, 2024, included $184.2 million of cash and cash equivalents, $2.5 million of restricted cash and $2,450.8 million of funds receivable and funds held on behalf of clients on the Condensed Consolidated Balance Sheet.
[3] Included in Investments on the Condensed Consolidated Balance Sheet