Restructuring - Summary of Restructuring Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	May 06, 2025
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	$ 4	$ 12	$ 44	$ 45
Inception to Date	180		180
Estimated Remaining Cost	25		25
Estimated Total Cost	205		205
Transformation Program
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	0	12	4	45
Inception to Date	140		140
Estimated Remaining Cost	0		0
Estimated Total Cost	140		140
Transformation Program \| Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	0	8	2	18
Inception to Date	45		45
Estimated Remaining Cost	0		0
Estimated Total Cost	45		45
Transformation Program \| Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	0	4	2	27
Inception to Date	95		95
Estimated Remaining Cost	0		0
Estimated Total Cost	95		95
Post-Separation Plan
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	4	0	40	0
Inception to Date	40		40
Estimated Remaining Cost	25		25
Estimated Total Cost	65		65		$ 65
Post-Separation Plan \| Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	0	0	20	0
Inception to Date	20		20
Estimated Remaining Cost	0		0
Estimated Total Cost	20		20		$ 20
Post-Separation Plan \| Other Restructuring Costs
Restructuring Cost And Reserve [Line Items]
Total Restructuring Costs	4	$ 0	20	$ 0
Inception to Date	20		20
Estimated Remaining Cost	25		25
Estimated Total Cost	$ 45		$ 45

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Alight, Inc. / Delaware 10-Q