Restructuring and Integration - Summary of Restructuring Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	$ 26
Inception to Date	26
Estimated Remaining Costs	114
Estimated Total Cost	140
Employer Solutions
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	20
Inception to Date	20
Estimated Remaining Costs	95
Estimated Total Cost	115
Employer Solutions | Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	1
Inception to Date	1
Estimated Remaining Costs	15
Estimated Total Cost	16
Employer Solutions | Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	19	[1]
Inception to Date	19	[1]
Estimated Remaining Costs	80	[1]
Estimated Total Cost	99	[1]
Professional Services
Restructuring Cost And Reserve [Line Items]
Restructuring Costs
Inception to Date
Estimated Remaining Costs	9
Estimated Total Cost	9
Professional Services | Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Costs
Inception to Date
Estimated Remaining Costs	5
Estimated Total Cost	5
Professional Services | Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Estimated Remaining Costs	4	[1]
Estimated Total Cost	4	[1]
Corporate
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	6
Inception to Date	6
Estimated Remaining Costs	10
Estimated Total Cost	16
Corporate | Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	5
Inception to Date	5
Estimated Remaining Costs	8
Estimated Total Cost	13
Corporate | Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	1	[1]
Inception to Date	1	[1]
Estimated Remaining Costs	2	[1]
Estimated Total Cost	$ 3	[1]

[1] Other restructuring costs associated with the Transformation Program primarily include data center exit costs, third party fees associated with the restructuring, and costs associated with transitioning existing technology and processes.