v3.25.4
BUSINESS SEGMENTS - Additional Information (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
segment
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Number of reporting segments | segment 4    
Total revenue $ 26,186 $ 25,100 $ 23,713
Operating income 4,141 3,767 3,864
Reimbursements      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total revenue [1] 19,204 18,482 17,413
Non-US | Reimbursements      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Operating income (54) (55) 23
Total segment      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total revenue 23,419 22,576 21,394
Total segment | Non-US      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total revenue 5,672 5,512 5,160
Operating income 1,382 1,329 1,258
Total segment | Non-US | Reimbursements      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total revenue $ 3,077 $ 3,018 $ 2,806
[1] See Note 15 for disclosure of related party amounts.