v3.26.3
Intangible Assets - Changes in Carrying Amount of Goodwill (Detail)
$ in Millions
 9 Months Ended
Sep. 30, 2026
USD ($)
Goodwill [Roll Forward]  
Beginning Balance $ 22,593
Goodwill acquired during the period 666
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3) 178
Foreign currency translation adjustments during the period (52)
Ending Balance 23,385
Brokerage  
Goodwill [Roll Forward]  
Beginning Balance 22,078
Goodwill acquired during the period 642
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3) 180
Foreign currency translation adjustments during the period (61)
Ending Balance 22,839
Risk Management  
Goodwill [Roll Forward]  
Beginning Balance 497
Goodwill acquired during the period 24
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3) (2)
Foreign currency translation adjustments during the period 11
Ending Balance 530
Corporate  
Goodwill [Roll Forward]  
Beginning Balance 18
Goodwill acquired during the period 0
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3) 0
Foreign currency translation adjustments during the period (2)
Ending Balance $ 16