Segment Reporting - Schedule of Current Reportable Segments by Segment Profit (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Segment Profit	$ 153	$ 132	$ 278	$ 416
Share-based compensation	15	1	5	5
Transaction and integration	3
Non-recurring professional expenses	17		18
Transformation initiatives				11
Restructuring	3	10	9	57
Other	2	4	(5)	28
Depreciation	14	24	49	66
Intangible amortization expense	74	51	100	151
Operating Income	25	42	102	98
Loss from change in fair value of financial instruments	90
Loss from change in fair value of tax receivable agreement	27
Interest expense	28	61	123	172
Other expense (income), net		3	9	(1)
Loss Before Income Tax (Benefit) Expense	(120)	(22)	(30)	(73)
Employer Solutions
Segment Reporting Information [Line Items]
Segment Profit	151	120	274	389
Professional Services
Segment Reporting Information [Line Items]
Segment Profit	4	$ 12	7	23
Hosted Business
Segment Reporting Information [Line Items]
Segment Profit	$ (2)		$ (3)	$ 4