Revenue - Schedule of Revenue by Geography (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 1,928	$ 1,952	$ 6,052	$ 6,205
Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,906	1,947	5,999	6,170
Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,906	1,947	5,999	6,170
Corporate, Non-Segment
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	7	(7)	18	(1)
Corporate, Non-Segment | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	3	3	15	9
HWC [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,172	1,177	3,576	3,606
HWC [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,156	1,164	3,533	3,566
HWC [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,156	1,164	3,533	3,566
R&B [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		749	774	2,458	2,532
R&B [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		747	772	2,451	2,527
R&B [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		747	772	2,451	2,527
Divested Businesses [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	8	0	68
Divested Businesses [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	8	0	68
Divested Businesses [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	8	0	68
North America [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,094	1,084	3,243	3,201
North America [Member] | Corporate, Non-Segment | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2	2	6	6
North America [Member] | HWC [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		766	748	2,301	2,258
North America [Member] | R&B [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		326	329	936	922
North America [Member] | Divested Businesses [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	5	0	15
Europe [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		583	635	2,067	2,275
Europe [Member] | Corporate, Non-Segment | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1	1	8	3
Europe [Member] | HWC [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		285	312	931	1,018
Europe [Member] | R&B [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		297	319	1,128	1,201
Europe [Member] | Divested Businesses [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	3	0	53
International [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		229	228	689	694
International [Member] | Corporate, Non-Segment | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0	1	0
International [Member] | HWC [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		105	104	301	290
International [Member] | R&B [Member] | Operating Segments [Member] | Service
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		124	124	387	404
International [Member] | Divested Businesses [Member] | Operating Segments [Member] | Service
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 and impacts from hedged revenue transactions.