v3.25.4
Restructuring Costs (Restructuring Activity) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Restructuring Reserve [Roll Forward]    
Restructuring charges $ 222 $ 276
Restructuring charges, statement of income or comprehensive income [Extensible Enumeration]   Operating Expenses
JLT Transaction    
Restructuring Reserve [Roll Forward]    
Beginning of period 117 $ 130
Restructuring charges 222 276
Cash payments (205) (270)
Non-cash charges (5) (19)
End of period 129 117
JLT Transaction | Severance    
Restructuring Reserve [Roll Forward]    
Beginning of period 75 89
Restructuring charges 174 163
Cash payments (150) (177)
Non-cash charges 0 0
End of period 99 75
JLT Transaction | Real Estate Related Costs    
Restructuring Reserve [Roll Forward]    
Beginning of period 42 39
Restructuring charges 32 66
Cash payments (39) (45)
Non-cash charges (5) (18)
End of period 30 42
JLT Transaction | Information Technology    
Restructuring Reserve [Roll Forward]    
Beginning of period 0 0
Restructuring charges 0 25
Cash payments 0 (24)
Non-cash charges 0 (1)
End of period 0 0
JLT Transaction | Consulting and Other Outside Services    
Restructuring Reserve [Roll Forward]    
Beginning of period 0 2
Restructuring charges 16 22
Cash payments (16) (24)
Non-cash charges 0 0
End of period $ 0 $ 0