Warrants to Acquire Shares of Common Stock - Changes in Fair Value of Warrant Liability (Details) $ in Thousands	9 Months Ended
Sep. 30, 2021 USD ($)
Class of Warrant or Right, Fair Value [Roll Forward]
Warrant liability, December 31, 2020	$ 55
Change in fair value of warrants	29
Warrant liability, September 30, 2021	$ 84

Fair value of warrant liabilities as of the balance sheet date.

No definition available.

Name:	sls_FairValueOfWarrantsLiabilities
Namespace Prefix:	sls_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant