v3.26.1
Equity-based Compensation - Schedule of Equity-based Compensation Expenses (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Equity-based compensation expense $ 6 $ 29 $ 16 $ 54
Location, Statement of Income, Balance [Axis]: us-gaap:GeneralAndAdministrativeExpense        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Equity-based compensation expense 6 29 16 54
Location, Statement of Income, Balance [Axis]: us-gaap:RestructuringCharges        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Equity-based compensation expense 0 0 0 0
Location, Statement of Income, Balance [Axis]: sybx:ResearchAndDevelopmentExpenseAndCredit        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Equity-based compensation expense $ 0 $ 0 $ 0 $ 0