Revenue - Schedule of Revenue by Geography (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 9,304	$ 8,726	$ 8,826
Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		9,202	8,649	8,783
Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		9,202	8,649	8,783
North America [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5,146	4,904	4,776
Europe [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		3,042	2,802	3,055
International [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,014	943	952
HWC [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5,625	5,312	5,291
HWC [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5,552	5,248	5,231
HWC [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5,552	5,248	5,231
HWC [Member] | North America [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		3,738	3,569	3,456
HWC [Member] | Europe [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,362	1,266	1,376
HWC [Member] | International [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		452	413	399
R&B [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		3,641	3,395	3,476
R&B [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		3,628	3,384	3,469
R&B [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		3,628	3,384	3,469
R&B [Member] | North America [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,400	1,328	1,295
R&B [Member] | Europe [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,668	1,527	1,623
R&B [Member] | International [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		560	529	551
Divested Businesses [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	71
Divested Businesses [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	71
Divested Businesses [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	71
Divested Businesses [Member] | North America [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	17
Divested Businesses [Member] | Europe [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	53
Divested Businesses [Member] | International [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	1
Corporate [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	38	19	(12)
Corporate [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	22	17	12
Corporate [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		22	17	12
Corporate [Member] | North America [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		8	7	8
Corporate [Member] | Europe [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		12	9	3
Corporate [Member] | International [Member] | Operating Segments [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2	$ 1	$ 1

[1] Reimbursable expenses and other, as well as Corporate revenue, are excluded from segment revenue, but included in total revenue on the consolidated statements of comprehensive income. Amounts included in Corporate revenue may include eliminations, adjustments to reserves and impacts from hedged revenue transactions.