Share-Based Compensation Expense - Schedule of Share-Based Compensation Costs Related to RSUs and PRSUs (Details) - RSUs and PRSUs[Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense	$ 54	$ 15		$ 129
Alight Holdings
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense			$ 5
Cost of services [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense	12	3		29
Cost of services [Member] | Alight Holdings
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense			1
Selling, general and administrative expenses [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense	$ 42	$ 12		$ 100
Selling, general and administrative expenses [Member] | Alight Holdings
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense			$ 4