CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS EQUITY (DEFICIT) (Parenthetical) - Series C redeemable convertible preferred stock $ in Thousands	3 Months Ended
Mar. 31, 2024 USD ($)
Derivative liability	$ 8,913
Offering costs	$ 382

The amount of derivative liability from issuance of temporary stock.

No definition available.

Name:	alms_TemporaryEquityDerivativeLiability
Namespace Prefix:	alms_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration