v3.26.1
Investments - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Schedule of Investments [Line Items]    
Deferred compensation liabilities [1] $ (8.4) $ (9.4)
Total 2,765.3 2,795.8
Money Market Funds [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [2] 2,726.2 2,759.2
Seed Capital Investments    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 33.7 26.4
Marketable Equity Securities [Member]    
Schedule of Investments [Line Items]    
Investments measured at fair value [3] 13.8 19.6
Quoted prices in Active Markets for Identical Assets (Level 1) [Member]    
Schedule of Investments [Line Items]    
Deferred compensation liabilities [1] (8.4) (9.4)
Total 2,765.3 2,795.8
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] 2,726.2 2,759.2
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] 33.7 26.4
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] 13.8 19.6
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 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 unaudited Condensed Consolidated Balance Sheets
[2] As of June 30, 2026, included $61.6 million of cash and cash equivalents, $1.2 million of restricted cash and $2,663.5 million of funds receivable and funds held on behalf of clients on the unaudited Condensed Consolidated Balance Sheets. As of December 31, 2025, included $76.6 million of cash and cash equivalents, $1.3 million of restricted cash and $2,681.3 million of funds receivable and funds held on behalf of clients on the unaudited Condensed Consolidated Balance Sheets.
[3] Included in investments on the unaudited Condensed Consolidated Balance Sheets