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
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense	$ 42		$ 75
Alight Holdings
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense		$ 3		$ 5
Cost of services [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense	10		17
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	$ 32		$ 58
Selling, general and administrative expenses [Member] | Alight Holdings
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total Share-based compensation expense		$ 3		$ 4