Segment Reporting - Schedule of Current Reportable Segments by Segment Profit (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Selling, general and administrative	$ 304		$ 754	$ 671
Depreciation and intangible amortization	163		339	339
Goodwill impairment			148
Operating Income (Loss)	65		(101)	(14)
(Gain) Loss from change in fair value of financial instruments	65		10	(38)
(Gain) loss from change in fair value of tax receivable agreement	(37)		118	(41)
Interest expense	57		131	122
Other (income) expense, net	3		6	(16)
Income (Loss) Before Taxes	(23)		(366)	(41)
Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit	532	$ 435	1,140	996
Selling, general and administrative	304	222	754	671
Depreciation and intangible amortization	163	111	339	339
Goodwill impairment	0	0	148	0
Operating Income (Loss)	65	102	(101)	(14)
(Gain) Loss from change in fair value of financial instruments	65	0	10	(38)
(Gain) loss from change in fair value of tax receivable agreement	(37)	0	118	(41)
Interest expense	57	123	131	122
Other (income) expense, net	3	9	6	(16)
Income (Loss) Before Taxes	(23)	(30)	(366)	(41)
Employer Solutions
Segment Reporting Information [Line Items]
Segment Profit	489	392	1,033	911
Professional Services
Segment Reporting Information [Line Items]
Segment Profit	44	46	109	86
Other
Segment Reporting Information [Line Items]
Segment Profit	$ (1)	$ (3)	$ (2)	$ (1)