Accounting Policies and Practices - Additional Information (Details)	3 Months Ended
Mar. 31, 2022
Accounting Policies And Practices [Line Items]
Business combination tax receivable agreement percentage of benefit deemed to realize	85.00%

Business combination tax receivable agreement percentage of benefit deemed to realize.

No definition available.

Name:	alit_BusinessCombinationTaxReceivableAgreementPercentageOfBenefitDeemedToRealize
Namespace Prefix:	alit_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration