v3.26.3
Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Financial instruments owned:    
Exchange traded equity securities $ 15 $ 12
Mutual funds 226 202
Money market funds 149 633
Total assets measured at fair value 390 847
Fiduciary Assets:    
Total fiduciary assets measured at fair value 297 322
Liabilities:    
Contingent purchase consideration liabilities 248 268
Total liabilities measured at fair value 248 268
Money market funds    
Fiduciary Assets:    
Total fiduciary assets measured at fair value 297 322
Identical Assets (Level 1)    
Financial instruments owned:    
Exchange traded equity securities 15 12
Mutual funds 226 202
Money market funds 149 633
Total assets measured at fair value 390 847
Fiduciary Assets:    
Total fiduciary assets measured at fair value 297 322
Liabilities:    
Contingent purchase consideration liabilities 0 0
Total liabilities measured at fair value 0 0
Identical Assets (Level 1) | Money market funds    
Fiduciary Assets:    
Total fiduciary assets measured at fair value 297 322
Observable Inputs (Level 2)    
Financial instruments owned:    
Exchange traded equity securities 0 0
Mutual funds 0 0
Money market funds 0 0
Total assets measured at fair value 0 0
Fiduciary Assets:    
Total fiduciary assets measured at fair value 0 0
Liabilities:    
Contingent purchase consideration liabilities 0 0
Total liabilities measured at fair value 0 0
Observable Inputs (Level 2) | Money market funds    
Fiduciary Assets:    
Total fiduciary assets measured at fair value 0 0
Unobservable Inputs (Level 3)    
Financial instruments owned:    
Exchange traded equity securities 0 0
Mutual funds 0 0
Money market funds 0 0
Total assets measured at fair value 0 0
Fiduciary Assets:    
Total fiduciary assets measured at fair value 0 0
Liabilities:    
Contingent purchase consideration liabilities 248 268
Total liabilities measured at fair value 248 268
Unobservable Inputs (Level 3) | Money market funds    
Fiduciary Assets:    
Total fiduciary assets measured at fair value $ 0 $ 0