Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Statement of Cash Flows [Abstract]
Accrued Expenses and Other current and Long-term Liabilities Related Party Amounts	$ (1,107)	$ 0

Accrued expenses and other current and long-term liabilities related party amounts.

No definition available.

Name:	mcrb_AccruedExpensesAndOtherCurrentAndLongTermLiabilitiesRelatedPartyAmounts
Namespace Prefix:	mcrb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration