Restructuring and Integration - Summary of Restructuring Costs (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($)		Jun. 30, 2023 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	$ 30		$ 56
Inception to Date	56		56
Estimated Remaining Costs	84		84
Estimated Total Cost	140		140
Employer Solutions
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	22		42
Inception to Date	42		42
Estimated Remaining Costs	68		68
Estimated Total Cost	110		110
Employer Solutions | Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	4		5
Inception to Date	5		5
Estimated Remaining Costs	10		10
Estimated Total Cost	15		15
Employer Solutions | Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	18	[1]	37	[1]
Inception to Date	37	[1]	37	[1]
Estimated Remaining Costs	58	[1]	58	[1]
Estimated Total Cost	95	[1]	95	[1]
Professional Services
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	1		1
Inception to Date	1		1
Estimated Remaining Costs	5		5
Estimated Total Cost	6		6
Professional Services | Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	1		1
Inception to Date	1		1
Estimated Remaining Costs	3		3
Estimated Total Cost	4		4
Professional Services | Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Estimated Remaining Costs	2	[1]	2	[1]
Estimated Total Cost	2	[1]	2	[1]
Corporate
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	7		13
Inception to Date	13		13
Estimated Remaining Costs	11		11
Estimated Total Cost	24		24
Corporate | Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Costs	7		12
Inception to Date	12		12
Estimated Remaining Costs	9		9
Estimated Total Cost	21		21
Corporate | Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Restructuring Costs			1	[1]
Inception to Date	1	[1]	1	[1]
Estimated Remaining Costs	2	[1]	2	[1]
Estimated Total Cost	$ 3	[1]	$ 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.