3.20.2 html 183 331 1 false 57 0 false 6 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://serestherapeutics.com/20200930/taxonomy/role/DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - Condensed Consolidated Balance Sheets Sheet http://serestherapeutics.com/20200930/taxonomy/role/StatementCondensedConsolidatedBalanceSheets Condensed Consolidated Balance Sheets Statements 2 false false R3.htm 100020 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://serestherapeutics.com/20200930/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParenthetical Condensed Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 100030 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss Sheet http://serestherapeutics.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLoss Condensed Consolidated Statements of Operations and Comprehensive Loss Statements 4 false false R5.htm 100040 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) Sheet http://serestherapeutics.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossParenthetical Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) Statements 5 false false R6.htm 100050 - Statement - Condensed Consolidated Statement of Stockholders' Equity (Deficit) Sheet http://serestherapeutics.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementOfStockholdersEquityDeficit Condensed Consolidated Statement of Stockholders' Equity (Deficit) Statements 6 false false R7.htm 100060 - Statement - Condensed Consolidated Statements of Cash Flows Sheet http://serestherapeutics.com/20200930/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlows Condensed Consolidated Statements of Cash Flows Statements 7 false false R8.htm 100070 - Disclosure - Nature of the Business and Basis of Presentation Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNatureOfBusinessAndBasisOfPresentation Nature of the Business and Basis of Presentation Notes 8 false false R9.htm 100080 - Disclosure - Summary of Significant Accounting Policies Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 9 false false R10.htm 100090 - Disclosure - Fair Value Measurements Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureFairValueMeasurements Fair Value Measurements Notes 10 false false R11.htm 100100 - Disclosure - Investments Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureInvestments Investments Notes 11 false false R12.htm 100110 - Disclosure - Property and Equipment, Net Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosurePropertyAndEquipmentNet Property and Equipment, Net Notes 12 false false R13.htm 100120 - Disclosure - Accrued Expenses and Other Current Liabilities Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities Accrued Expenses and Other Current Liabilities Notes 13 false false R14.htm 100130 - Disclosure - Restructuring Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureRestructuring Restructuring Notes 14 false false R15.htm 100140 - Disclosure - Note Payable Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNotePayable Note Payable Notes 15 false false R16.htm 100150 - Disclosure - Common Stock and Stock-Based Awards Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwards Common Stock and Stock-Based Awards Notes 16 false false R17.htm 100160 - Disclosure - Collaboration Revenue Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCollaborationRevenue Collaboration Revenue Notes 17 false false R18.htm 100170 - Disclosure - Commitments and Contingencies Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 18 false false R19.htm 100180 - Disclosure - Income Taxes Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureIncomeTaxes Income Taxes Notes 19 false false R20.htm 100190 - Disclosure - Related Party Transactions Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureRelatedPartyTransactions Related Party Transactions Notes 20 false false R21.htm 100200 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 21 false false R22.htm 100210 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 22 false false R23.htm 100220 - Disclosure - Fair Value Measurements (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureFairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureFairValueMeasurements 23 false false R24.htm 100230 - Disclosure - Investments (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureInvestmentsTables Investments (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureInvestments 24 false false R25.htm 100240 - Disclosure - Property and Equipment, Net (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosurePropertyAndEquipmentNetTables Property and Equipment, Net (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosurePropertyAndEquipmentNet 25 false false R26.htm 100250 - Disclosure - Accrued Expenses and Other Current Liabilities (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables Accrued Expenses and Other Current Liabilities (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities 26 false false R27.htm 100260 - Disclosure - Note Payable (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNotePayableTables Note Payable (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNotePayable 27 false false R28.htm 100270 - Disclosure - Common Stock and Stock-Based Awards (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwardsTables Common Stock and Stock-Based Awards (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwards 28 false false R29.htm 100280 - Disclosure - Collaboration Revenue (Tables) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCollaborationRevenueTables Collaboration Revenue (Tables) Tables http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCollaborationRevenue 29 false false R30.htm 100290 - Disclosure - Nature of the Business and Basis of Presentation - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNatureOfBusinessAndBasisOfPresentationAdditionalInformationDetail Nature of the Business and Basis of Presentation - Additional Information (Detail) Details 30 false false R31.htm 100300 - Disclosure - Summary of Significant Accounting Policies - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesSummaryOfPotentialCommonSharesExcludedFromCalculationOfDilutedNetLossPerShareDetail Summary of Significant Accounting Policies - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share (Detail) Details 31 false false R32.htm 100310 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail Summary of Significant Accounting Policies - Additional Information (Detail) Details 32 false false R33.htm 100320 - Disclosure - Fair Value Measurements - Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfFairValueHierarchyForAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetail Fair Value Measurements - Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) Details 33 false false R34.htm 100330 - Disclosure - Fair Value Measurements - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureFairValueMeasurementsAdditionalInformationDetail Fair Value Measurements - Additional Information (Detail) Details 34 false false R35.htm 100340 - Disclosure - Investments - Schedule of Investments by Security Type (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureInvestmentsScheduleOfInvestmentsBySecurityTypeDetail Investments - Schedule of Investments by Security Type (Detail) Details 35 false false R36.htm 100350 - Disclosure - Investments - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureInvestmentsAdditionalInformationDetail Investments - Additional Information (Detail) Details 36 false false R37.htm 100360 - Disclosure - Investments - Schedule of Amortized Cost and Fair Value of Investments by Contractual Maturity (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureInvestmentsScheduleOfAmortizedCostAndFairValueOfInvestmentsByContractualMaturityDetail Investments - Schedule of Amortized Cost and Fair Value of Investments by Contractual Maturity (Detail) Details 37 false false R38.htm 100370 - Disclosure - Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosurePropertyAndEquipmentNetScheduleOfPropertyAndEquipmentNetDetail Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) Details 38 false false R39.htm 100380 - Disclosure - Property and Equipment, Net - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosurePropertyAndEquipmentNetAdditionalInformationDetail Property and Equipment, Net - Additional Information (Detail) Details 39 false false R40.htm 100390 - Disclosure - Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesSummaryOfAccruedExpensesAndOtherCurrentLiabilitiesDetail Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) Details 40 false false R41.htm 100400 - Disclosure - Restructuring - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureRestructuringAdditionalInformationDetail Restructuring - Additional Information (Detail) Details 41 false false R42.htm 100410 - Disclosure - Note Payable - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNotePayableAdditionalInformationDetail Note Payable - Additional Information (Detail) Details 42 false false R43.htm 100420 - Disclosure - Note Payable - Summary of Future Principal Payments Due Under Arrangement, Excluding Interest and End of Term Charge (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureNotePayableSummaryOfFuturePrincipalPaymentsDueUnderArrangementExcludingInterestAndEndOfTermChargeDetail Note Payable - Summary of Future Principal Payments Due Under Arrangement, Excluding Interest and End of Term Charge (Detail) Details 43 false false R44.htm 100430 - Disclosure - Common Stock and Stock-Based Awards - Common Stock - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwardsCommonStockAdditionalInformationDetail Common Stock and Stock-Based Awards - Common Stock - Additional Information (Detail) Details 44 false false R45.htm 100440 - Disclosure - Common Stock and Stock-Based Awards - Summary of Stock Option Activity (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwardsSummaryOfStockOptionActivityDetail Common Stock and Stock-Based Awards - Summary of Stock Option Activity (Detail) Details 45 false false R46.htm 100450 - Disclosure - Common Stock and Stock-Based Awards - Stock Options - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwardsStockOptionsAdditionalInformationDetail Common Stock and Stock-Based Awards - Stock Options - Additional Information (Detail) Details 46 false false R47.htm 100460 - Disclosure - Common Stock and Stock-Based Awards - Summary of Restricted Stock Unit Activity (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwardsSummaryOfRestrictedStockUnitActivityDetail Common Stock and Stock-Based Awards - Summary of Restricted Stock Unit Activity (Detail) Details 47 false false R48.htm 100470 - Disclosure - Common Stock and Stock-Based Awards - Summary of Stock Based Compensation Expense (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommonStockAndStockBasedAwardsSummaryOfStockBasedCompensationExpenseDetail Common Stock and Stock-Based Awards - Summary of Stock Based Compensation Expense (Detail) Details 48 false false R49.htm 100480 - Disclosure - Collaboration Revenue - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCollaborationRevenueAdditionalInformationDetail Collaboration Revenue - Additional Information (Detail) Details 49 false false R50.htm 100490 - Disclosure - Collaboration Revenue - Changes in Contract Liabilities (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCollaborationRevenueChangesInContractLiabilitiesDetail Collaboration Revenue - Changes in Contract Liabilities (Detail) Details 50 false false R51.htm 100500 - Disclosure - Collaboration Revenue - Schedule of Revenue Recognized (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCollaborationRevenueScheduleOfRevenueRecognizedDetail Collaboration Revenue - Schedule of Revenue Recognized (Detail) Details 51 false false R52.htm 100510 - Disclosure - Commitments and Contingencies - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail Commitments and Contingencies - Additional Information (Detail) Details 52 false false R53.htm 100520 - Disclosure - Income Taxes - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetail Income Taxes - Additional Information (Detail) Details 53 false false R54.htm 100530 - Disclosure - Related Party Transactions - Additional Information (Detail) Sheet http://serestherapeutics.com/20200930/taxonomy/role/DisclosureRelatedPartyTransactionsAdditionalInformationDetail Related Party Transactions - Additional Information (Detail) Details 54 false false All Reports Book All Reports mcrb-10q_20200930.htm mcrb-20200930.xsd mcrb-20200930_cal.xml mcrb-20200930_def.xml mcrb-20200930_lab.xml mcrb-20200930_pre.xml mcrb-ex101_219.htm mcrb-ex311_11.htm mcrb-ex312_7.htm mcrb-ex321_6.htm mcrb-ex322_8.htm http://xbrl.sec.gov/dei/2019-01-31 http://fasb.org/us-gaap/2020-01-31 http://fasb.org/srt/2020-01-31 true true