v3.26.1
Revenue - Schedule of Revenue by Geography (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax $ 2,363 $ 2,180
Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 2,341 2,159
Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 2,341 2,159
HWC [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,275 1,173
HWC [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,256 1,156
HWC [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,256 1,156
R&B [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,086 1,006
R&B [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,083 1,003
R&B [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,083 1,003
Corporate [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax [1] 2 1
Corporate [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax [1] 2 0
Corporate [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 2 0
North America [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,020 971
North America [Member] | HWC [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 673 645
North America [Member] | R&B [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 347 326
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
Europe [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 1,038 929
Europe [Member] | HWC [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 444 391
Europe [Member] | R&B [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 592 538
Europe [Member] | Corporate [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 2 0
International [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 283 259
International [Member] | HWC [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 139 120
International [Member] | R&B [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax 144 139
International [Member] | Corporate [Member] | Operating Segments [Member] | Service [Member]    
Disaggregation Of Revenue [Line Items]    
Revenue from Contract with Customer, Excluding Assessed Tax $ 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.