Debt - Additional Information (Details) - USD ($)		1 Months Ended							3 Months Ended
		Mar. 31, 2023	Jan. 31, 2022	Aug. 31, 2021	Jul. 31, 2021	Aug. 31, 2020	May 31, 2020	May 31, 2017	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Debt Instrument [Line Items]
Debt balance		$ 2,816,000,000							$ 2,816,000,000		$ 2,823,000,000
Amortization of financing fees and benefits									(1,000,000)	$ (1,000,000)
Interest expense related to debt instruments									51,000,000	27,000,000
Interest Expense
Debt Instrument [Line Items]
Amortization of financing fees and benefits									$ 1,000,000	1,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Increase in revolving credit facility		300,000,000
Revolving Credit Facility | Alight Holdings
Debt Instrument [Line Items]
Debt term								5 years
Maturity Date								May 01, 2022
Line of credit, maximum borrowing capacity								$ 250,000,000
Amended Revolving Credit Facility
Debt Instrument [Line Items]
Maturity Date				Aug. 31, 2026					Aug. 31, 2026
Line of credit, maximum borrowing capacity		300,000,000		$ 294,000,000					$ 300,000,000
Unused letters of credit		$ 3,000,000							3,000,000
Proceeds from Lines of Credit									$ 0
Amended Revolving Credit Facility | Alight Holdings
Debt Instrument [Line Items]
Maturity Date						Oct. 31, 2024
Line of credit, maximum borrowing capacity						$ 226,000,000
Term Loan
Debt Instrument [Line Items]
Maturity Date									May 01, 2024
Repayment of principal					$ 556,000,000
Term Loan | Alight Holdings
Debt Instrument [Line Items]
Debt term		7 years						7 years
Repayments of principal to refinance debt						270,000,000
Term Loan, Amended
Debt Instrument [Line Items]
Payment terms									The Company is required to make principal payments at the end of each fiscal quarter based on defined terms in the agreement with the remaining principal balances due on the maturity dates.
Principal payment									$ 6,000,000	$ 8,000,000
Swap agreement expiration period									2026-12
Term Loan, Amended | Alight Holdings
Debt Instrument [Line Items]
Debt balance						$ 1,986,000,000
Maturity Date						Oct. 31, 2026
Term Loan, Amended | Minimum | Alight Holdings
Debt Instrument [Line Items]
Debt instrument, variable interest rate						0.50%
Term Loan, Third Incremental
Debt Instrument [Line Items]
Debt balance				$ 525,000,000
Maturity Date			Aug. 31, 2028	Aug. 31, 2028
Secured Senior Notes
Debt Instrument [Line Items]
Maturity Date									Jun. 01, 2025
Payment terms									interest at a fixed rate of 5.75% per annum, payable semi-annually on June 1 and December 1 of each year
Secured Senior Notes | Alight Holdings
Debt Instrument [Line Items]
Maturity Date							Jun. 01, 2025
Face amount							$ 300,000,000
Interest rate							5.75%
Debt payment beginning date							Dec. 01, 2020
Term Loan, B-1
Debt Instrument [Line Items]
Maturity Date	[1]								Aug. 31, 2028
Increase in term loan		$ 65,000,000
Term Loan, B-1 | SOFR | Alight Holdings
Debt Instrument [Line Items]
Debt instrument, variable interest rate						3.00%

[1] The net balance for the B-1 Term Loan at March 31, 2023 includes unamortized debt issuance costs of $9 million. The net balance for the B-1 Term Loan at December 31, 2022 includes unamortized debt issuance costs of $8 million.