v3.26.1
Segment Information - Revenue (Net of Reimbursable Expenses) of the Reported Segments (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Segment Reporting Information [Line Items]    
Total revenue $ 2,412 $ 2,223
Depreciation 56 54
Income from operations 448 432
HWC [Member]    
Segment Reporting Information [Line Items]    
Total revenue 1,284 1,182
R&B [Member]    
Segment Reporting Information [Line Items]    
Total revenue 1,119 1,030
Operating Segments [Member]    
Segment Reporting Information [Line Items]    
Segment revenue excluding interest income 2,348 2,163
Interest income 33 29
Total revenue 2,381 2,192
Other segment expense 1,741 1,614
Depreciation 42 41
Total segment expense 1,783 1,655
Income from operations 598 537
Operating Segments [Member] | HWC [Member]    
Segment Reporting Information [Line Items]    
Segment revenue excluding interest income 1,257 1,158
Interest income 8 7
Total revenue 1,265 1,165
Other segment expense 887 823
Depreciation 32 31
Total segment expense 919 854
Income from operations 346 311
Operating Segments [Member] | R&B [Member]    
Segment Reporting Information [Line Items]    
Segment revenue excluding interest income 1,091 1,005
Interest income 25 22
Total revenue 1,116 1,027
Other segment expense 854 791
Depreciation 10 10
Total segment expense 864 801
Income from operations $ 252 $ 226