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, 2022	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2022
Segment Reporting Information [Line Items]
Segment Profit		$ 133	$ 153		$ 417
Share-based compensation		54	15		129
Transaction and integration expenses	[1]	2	3		11
Non-recurring professional expenses	[2]		17
Restructuring		23	3		43
Other	[3]	5	2		16
Depreciation		21	14		56
Intangible amortization expense		78	74		237
Operating (Loss) Income		(50)	25		(75)
Loss (Gain) from change in fair value of financial instruments		10	90		(53)
(Gain) loss from change in fair value of tax receivable agreement		(20)	27		(63)
Interest expense		31	28		89
Other (income) expense, net		(6)			(14)
Loss Before Income Tax Benefit		(65)	(120)		(34)
Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit				$ 278
Share-based compensation				5
Non-recurring professional expenses	[2]			18
Restructuring				9
Other	[3]			(5)
Depreciation				49
Intangible amortization expense				100
Operating (Loss) Income				102
Interest expense				123
Other (income) expense, net				9
Loss Before Income Tax Benefit				(30)
Employer Solutions
Segment Reporting Information [Line Items]
Segment Profit		130	151		419
Employer Solutions | Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit				274
Professional Services
Segment Reporting Information [Line Items]
Segment Profit		$ 3	4
Professional Services | Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit				7
Hosted Business
Segment Reporting Information [Line Items]
Segment Profit			$ (2)		$ (2)
Hosted Business | Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit				$ (3)

[1] Transaction and integration expenses includes activity related to acquisitions.

[2] Non-recurring professional expenses includes external advisor and legal costs related to the Company’s Business Combination completed in 2021.

[3] For the Successor three and nine months ended September 30, 2022, Other primarily includes expenses related to debt refinancing completed in the first quarter of 2022 and other non-operational activities, offset by Other income, net. For the Successor three months ended September 30, 2021 and the Predecessor six months ended June 30, 2021, Other includes long-term incentive expenses, offset by Other expense, net.