Segment Reporting - Schedule of Current Reportable and Recast of Segments by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Revenue	$ 806	$ 715	$ 1,637	$ 1,440
Employer Solutions
Segment Reporting Information [Line Items]
Revenue	697	614	1,420	1,237
Employer Solutions | Recurring
Segment Reporting Information [Line Items]
Revenue	639	559	1,308	1,129
Employer Solutions | Project
Segment Reporting Information [Line Items]
Revenue	58	55	112	108
Professional Services
Segment Reporting Information [Line Items]
Revenue	100	91	198	181
Professional Services | Recurring
Segment Reporting Information [Line Items]
Revenue	35	32	68	62
Professional Services | Project
Segment Reporting Information [Line Items]
Revenue	65	59	130	119
Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue	797	705	1,618	1,418
Other
Segment Reporting Information [Line Items]
Revenue	$ 9	$ 10	$ 19	$ 22