Revenue from contracts with customers - Schedule of Deferred Revenue from customers (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2023 USD ($)
Revenue from Contract with Customer [Abstract]
Deferred revenue from customers as of January 1	$ 700
Revenue from customers recognized in the period	(140)
Deferred revenue from customers as of March 31	$ 560

Contract with customer liability deferred revenue recognized.

No definition available.

Name:	algs_ContractWithCustomerLiabilityDeferredRevenueRecognized
Namespace Prefix:	algs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration