v3.26.1
Accelerating Aon United Program - Schedule of Changes in the Company’s Liabilities for the Program (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Restructuring Reserve [Roll Forward]        
Charges $ 96 $ 94 $ 188 $ 204
Accelerating Aon United Program        
Restructuring Reserve [Roll Forward]        
Liability balance as of December 31, 2025     147  
Charges 96 $ 94 188 $ 204
Cash payments     (164)  
Foreign currency translation and other     (2)  
Non-cash charges     0  
Liability balance as of June 30, 2026 169   169  
Total costs incurred from inception to date 1,077   1,077  
Accelerating Aon United Program | Technology and other        
Restructuring Reserve [Roll Forward]        
Liability balance as of December 31, 2025     39  
Charges     124  
Cash payments     (105)  
Foreign currency translation and other     0  
Non-cash charges     (2)  
Liability balance as of June 30, 2026 56   56  
Total costs incurred from inception to date 459   459  
Accelerating Aon United Program | Workforce optimization        
Restructuring Reserve [Roll Forward]        
Liability balance as of December 31, 2025     108  
Charges     61  
Cash payments     (59)  
Foreign currency translation and other     (2)  
Non-cash charges     5  
Liability balance as of June 30, 2026 113   113  
Total costs incurred from inception to date 516   516  
Accelerating Aon United Program | Asset impairments        
Restructuring Reserve [Roll Forward]        
Liability balance as of December 31, 2025     0  
Charges     3  
Cash payments     0  
Foreign currency translation and other     0  
Non-cash charges     (3)  
Liability balance as of June 30, 2026 0   0  
Total costs incurred from inception to date $ 102   $ 102