Debt - Additional Information (Details) - USD ($)		1 Months Ended					3 Months Ended
	May 31, 2024	Jan. 31, 2025	Dec. 31, 2024	Jul. 31, 2024	Jun. 30, 2024	Mar. 31, 2023	Mar. 31, 2025	Mar. 31, 2024	Aug. 31, 2021
Debt Instrument [Line Items]
Debt balance			$ 2,025,000,000				$ 2,019,000,000
Interest expense related to debt instruments							32,000,000	$ 55,000,000
$300 million Revolving Credit Facility, Amended
Debt Instrument [Line Items]
Debt balance			0				0
Line of credit, maximum borrowing capacity							300,000,000		$ 294,000,000
Unused letters of credit							0
Revolving credit facility, borrowings							0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Increase in revolving credit facility						$ 300,000,000
Sixth Incremental Term Loans
Debt Instrument [Line Items]
Debt balance			$ 2,025,000,000		$ 2,489,000,000		0
Repayments of debt				$ 440,000,000
Sixth Incremental Term Loans | Alight Holdings
Debt Instrument [Line Items]
Debt instrument, variable interest rate			2.25%		2.25%
Fifth Incremental Term Loans | Alight Holdings
Debt Instrument [Line Items]
Debt instrument, variable interest rate	2.75%
Seventh Incremental Term Loans
Debt Instrument [Line Items]
Debt balance			$ 0				2,019,000,000
Face amount		$ 2,030,000,000
Seventh Incremental Term Loans | Alight Holdings
Debt Instrument [Line Items]
Debt instrument, variable interest rate		1.75%
Term Loan, Amended
Debt Instrument [Line Items]
Principal payment							$ 5,000,000	$ 6,000,000