v3.26.3
Revenue - Schedule of Revenue by Geography (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax $ 2,404 $ 2,240 $ 7,195 $ 6,635
Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 2,383 2,226 7,123 6,577
Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 2,383 2,226 7,123 6,577
HWC [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,362 1,269 3,921 3,632
HWC [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,341 1,253 3,859 3,581
HWC [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,341 1,253 3,859 3,581
R&B [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,047 976 3,274 3,004
R&B [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,042 973 3,262 2,995
R&B [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,042 973 3,262 2,995
Corporate [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax [1] (5) (5) 0 (1)
Corporate [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax [1] 0 0 2 1
Corporate [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 0 0 2 1
North America [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,195 1,084 3,396 3,122
North America [Member] | HWC [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 761 719 2,146 2,029
North America [Member] | R&B [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 434 365 1,250 1,092
North America [Member] | Corporate [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 0 0 0 1
Europe [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 866 857 2,811 2,632
Europe [Member] | HWC [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 428 400 1,291 1,183
Europe [Member] | R&B [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 438 457 1,518 1,449
Europe [Member] | Corporate [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 0 0 2 0
International [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 322 285 916 823
International [Member] | HWC [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 152 134 422 369
International [Member] | R&B [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 170 151 494 454
International [Member] | Corporate [Member] | Operating Segments [Member] | Service [Member]        
Disaggregation Of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax $ 0 $ 0 $ 0 $ 0
[1] Reimbursable expenses and other, as well as Corporate revenue, are excluded from segment revenue, but included in total revenue on the condensed consolidated statements of comprehensive income. Amounts included in Corporate revenue may include eliminations, adjustments to reserves and impacts from hedged revenue transactions.