Segment Reporting - Additional Information (Details) - Customer	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Segment Reporting [Abstract]
Number of single client comprising more than 10% of revenues	0	0

Number of single client comprising more than ten percent of revenues.

No definition available.

Name:	alit_NumberOfSingleClientComprisingMoreThanTenPercentOfRevenues
Namespace Prefix:	alit_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration