3.3.1.900 html 185 313 1 false 59 0 false 5 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://serestherapeutics.com/20151231/taxonomy/role/DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - Consolidated Balance Sheets Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedBalanceSheets Consolidated Balance Sheets Statements 2 false false R3.htm 100020 - Statement - Consolidated Balance Sheets (Parenthetical) Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedBalanceSheetsParenthetical Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 100030 - Statement - Consolidated Statements of Operations and Comprehensive Loss Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedStatementsOfOperationsAndComprehensiveLoss Consolidated Statements of Operations and Comprehensive Loss Statements 4 false false R5.htm 100040 - Statement - Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedStatementsOfOperationsAndComprehensiveLossParenthetical Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) Statements 5 false false R6.htm 100050 - Statement - Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedStatementsOfConvertiblePreferredStockAndStockholdersEquityDeficit Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) Statements 6 false false R7.htm 100060 - Statement - Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedStatementsOfConvertiblePreferredStockAndStockholdersEquityDeficitParenthetical Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) Statements 7 false false R8.htm 100070 - Statement - Consolidated Statements of Cash Flows Sheet http://serestherapeutics.com/20151231/taxonomy/role/StatementConsolidatedStatementsOfCashFlows Consolidated Statements of Cash Flows Statements 8 false false R9.htm 100080 - Disclosure - Nature of the Business and Basis of Presentation Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNatureOfBusinessAndBasisOfPresentation Nature of the Business and Basis of Presentation Notes 9 false false R10.htm 100090 - Disclosure - Summary of Significant Accounting Policies Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 10 false false R11.htm 100100 - Disclosure - Fair Value of Financial Assets and Liabilities Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureFairValueOfFinancialAssetsAndLiabilities Fair Value of Financial Assets and Liabilities Notes 11 false false R12.htm 100110 - Disclosure - Investments Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureInvestments Investments Notes 12 false false R13.htm 100120 - Disclosure - Property and Equipment, Net Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentNet Property and Equipment, Net Notes 13 false false R14.htm 100130 - Disclosure - Accrued Expenses and Other Current Liabilities Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities Accrued Expenses and Other Current Liabilities Notes 14 false false R15.htm 100140 - Disclosure - Notes Payable Notes http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNotesPayable Notes Payable Notes 15 false false R16.htm 100150 - Disclosure - Preferred Stock Warrant Liability Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePreferredStockWarrantLiability Preferred Stock Warrant Liability Notes 16 false false R17.htm 100160 - Disclosure - Convertible Preferred Stock Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStock Convertible Preferred Stock Notes 17 false false R18.htm 100170 - Disclosure - Stockholders??? Equity (Deficit) Common Stock Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStock Stockholders??? Equity (Deficit) Common Stock Notes 18 false false R19.htm 100180 - Disclosure - Net Loss per Share Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNetLossPerShare Net Loss per Share Notes 19 false false R20.htm 100190 - Disclosure - Commitments and Contingencies Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 20 false false R21.htm 100200 - Disclosure - Income Taxes Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxes Income Taxes Notes 21 false false R22.htm 100210 - Disclosure - Selected Quarterly Financial Data (Unaudited) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSelectedQuarterlyFinancialDataUnaudited Selected Quarterly Financial Data (Unaudited) Notes 22 false false R23.htm 100220 - Disclosure - Related Party Transactions Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureRelatedPartyTransactions Related Party Transactions Notes 23 false false R24.htm 100230 - Disclosure - 401(k) Savings Plan Sheet http://serestherapeutics.com/20151231/taxonomy/role/Disclosure401KSavingsPlan 401(k) Savings Plan Notes 24 false false R25.htm 100240 - Disclosure - Subsequent Events Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSubsequentEvents Subsequent Events Notes 25 false false R26.htm 100250 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 26 false false R27.htm 100260 - Disclosure - Fair Value of Financial Assets and Liabilities (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureFairValueOfFinancialAssetsAndLiabilitiesTables Fair Value of Financial Assets and Liabilities (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureFairValueOfFinancialAssetsAndLiabilities 27 false false R28.htm 100270 - Disclosure - Investments (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureInvestmentsTables Investments (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureInvestments 28 false false R29.htm 100280 - Disclosure - Property and Equipment, Net (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentNetTables Property and Equipment, Net (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentNet 29 false false R30.htm 100290 - Disclosure - Accrued Expenses and Other Current Liabilities (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables Accrued Expenses and Other Current Liabilities (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities 30 false false R31.htm 100300 - Disclosure - Preferred Stock Warrant Liability (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePreferredStockWarrantLiabilityTables Preferred Stock Warrant Liability (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePreferredStockWarrantLiability 31 false false R32.htm 100310 - Disclosure - Stockholders??? Equity (Deficit) Common Stock (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockTables Stockholders??? Equity (Deficit) Common Stock (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStock 32 false false R33.htm 100320 - Disclosure - Net Loss per Share (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNetLossPerShareTables Net Loss per Share (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNetLossPerShare 33 false false R34.htm 100330 - Disclosure - Commitments and Contingencies (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingenciesTables Commitments and Contingencies (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingencies 34 false false R35.htm 100340 - Disclosure - Income Taxes (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxesTables Income Taxes (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxes 35 false false R36.htm 100350 - Disclosure - Selected Quarterly Financial Data (Unaudited) (Tables) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSelectedQuarterlyFinancialDataUnauditedTables Selected Quarterly Financial Data (Unaudited) (Tables) Tables http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSelectedQuarterlyFinancialDataUnaudited 36 false false R37.htm 100360 - Disclosure - Nature of the Business and Basis of Presentation - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNatureOfBusinessAndBasisOfPresentationAdditionalInformationDetail Nature of the Business and Basis of Presentation - Additional Information (Detail) Details 37 false false R38.htm 100370 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail Summary of Significant Accounting Policies - Additional Information (Detail) Details 38 false false R39.htm 100380 - Disclosure - Fair Value of Financial Assets and Liability - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureFairValueOfFinancialAssetsAndLiabilitySummaryOfAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetail Fair Value of Financial Assets and Liability - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) Details 39 false false R40.htm 100390 - Disclosure - Fair Value of Financial Assets and Liabilities - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureFairValueOfFinancialAssetsAndLiabilitiesAdditionalInformationDetail Fair Value of Financial Assets and Liabilities - Additional Information (Detail) Details 40 false false R41.htm 100400 - Disclosure - Investments - Schedule of Fair Value of Available-for-Sale Investments by Type of Security (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureInvestmentsScheduleOfFairValueOfAvailableForSaleInvestmentsByTypeOfSecurityDetail Investments - Schedule of Fair Value of Available-for-Sale Investments by Type of Security (Detail) Details 41 false false R42.htm 100410 - Disclosure - Investments - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureInvestmentsAdditionalInformationDetail Investments - Additional Information (Detail) Details 42 false false R43.htm 100420 - Disclosure - Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentNetScheduleOfPropertyAndEquipmentNetDetail Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) Details 43 false false R44.htm 100430 - Disclosure - Property and Equipment, Net - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentNetAdditionalInformationDetail Property and Equipment, Net - Additional Information (Detail) Details 44 false false R45.htm 100440 - Disclosure - Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesSummaryOfAccruedExpensesAndOtherCurrentLiabilitiesDetail Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) Details 45 false false R46.htm 100450 - Disclosure - Notes Payable - Additional Information (Detail) Notes http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNotesPayableAdditionalInformationDetail Notes Payable - Additional Information (Detail) Details 46 false false R47.htm 100460 - Disclosure - Preferred Stock Warrant Liability - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePreferredStockWarrantLiabilityAdditionalInformationDetail Preferred Stock Warrant Liability - Additional Information (Detail) Details 47 false false R48.htm 100470 - Disclosure - Preferred Stock Warrant Liability - Summary of Assumptions and Inputs Used in Determining Fair Value of Preferred Stock Warrant Liability Valued Using Black-Scholes Option-Pricing Model (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePreferredStockWarrantLiabilitySummaryOfAssumptionsAndInputsUsedInDeterminingFairValueOfPreferredStockWarrantLiabilityValuedUsingBlackScholesOptionPricingModelDetail Preferred Stock Warrant Liability - Summary of Assumptions and Inputs Used in Determining Fair Value of Preferred Stock Warrant Liability Valued Using Black-Scholes Option-Pricing Model (Detail) Details 48 false false R49.htm 100480 - Disclosure - Preferred Stock Warrant Liability - Summary of Rollforward of Fair Value of Preferred Stock Warrant Liability (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosurePreferredStockWarrantLiabilitySummaryOfRollforwardOfFairValueOfPreferredStockWarrantLiabilityDetail Preferred Stock Warrant Liability - Summary of Rollforward of Fair Value of Preferred Stock Warrant Liability (Detail) Details 49 false false R50.htm 100490 - Disclosure - Convertible Preferred Stock - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStockAdditionalInformationDetail Convertible Preferred Stock - Additional Information (Detail) Details 50 false false R51.htm 100500 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - Additional Information (Detail) Details 51 false false R52.htm 100510 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Common Stock Warrants - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockCommonStockWarrantsAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - Common Stock Warrants - Additional Information (Detail) Details 52 false false R53.htm 100520 - Disclosure - Stockholders' Equity (Deficit) Common Stock - 2012 Stock Incentive plan - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStock2012StockIncentivePlanAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - 2012 Stock Incentive plan - Additional Information (Detail) Details 53 false false R54.htm 100530 - Disclosure - Stockholders' Equity (Deficit) Common Stock - 2015 Incentive Award Plan - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStock2015IncentiveAwardPlanAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - 2015 Incentive Award Plan - Additional Information (Detail) Details 54 false false R55.htm 100540 - Disclosure - Stockholders' Equity (Deficit) Common Stock - 2015 Employee Stock Purchase Plan - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStock2015EmployeeStockPurchasePlanAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - 2015 Employee Stock Purchase Plan - Additional Information (Detail) Details 55 false false R56.htm 100550 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Summary of Estimated Fair Value of Employee Stock Options (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockSummaryOfEstimatedFairValueOfEmployeeStockOptionsDetail Stockholders' Equity (Deficit) Common Stock - Summary of Estimated Fair Value of Employee Stock Options (Detail) Details 56 false false R57.htm 100560 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Summary of Stock Option Activity (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockSummaryOfStockOptionActivityDetail Stockholders' Equity (Deficit) Common Stock - Summary of Stock Option Activity (Detail) Details 57 false false R58.htm 100570 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Stock Options - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockStockOptionsAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - Stock Options - Additional Information (Detail) Details 58 false false R59.htm 100580 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Summary of Restricted Stock Activity (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockSummaryOfRestrictedStockActivityDetail Stockholders' Equity (Deficit) Common Stock - Summary of Restricted Stock Activity (Detail) Details 59 false false R60.htm 100590 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Restricted Common Stock - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockRestrictedCommonStockAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - Restricted Common Stock - Additional Information (Detail) Details 60 false false R61.htm 100600 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Summary of Stock Based Compensation Expense (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockSummaryOfStockBasedCompensationExpenseDetail Stockholders' Equity (Deficit) Common Stock - Summary of Stock Based Compensation Expense (Detail) Details 61 false false R62.htm 100610 - Disclosure - Stockholders' Equity (Deficit) Common Stock - Stock Based Compensation - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureStockholdersEquityDeficitCommonStockStockBasedCompensationAdditionalInformationDetail Stockholders' Equity (Deficit) Common Stock - Stock Based Compensation - Additional Information (Detail) Details 62 false false R63.htm 100620 - Disclosure - Net Loss per Share - Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNetLossPerShareBasicAndDilutedNetLossPerShareAttributableToCommonStockholdersDetail Net Loss per Share - Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) Details 63 false false R64.htm 100630 - Disclosure - Net Loss per Share - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureNetLossPerShareSummaryOfPotentialCommonSharesExcludedFromCalculationOfDilutedNetLossPerShareDetail Net Loss per Share - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share (Detail) Details 64 false false R65.htm 100640 - Disclosure - Commitments and Contingencies - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail Commitments and Contingencies - Additional Information (Detail) Details 65 false false R66.htm 100650 - Disclosure - Commitments and Contingencies - Summary Of Future Minimum Lease Payments For Operating Leases (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingenciesSummaryOfFutureMinimumLeasePaymentsForOperatingLeasesDetail Commitments and Contingencies - Summary Of Future Minimum Lease Payments For Operating Leases (Detail) Details 66 false false R67.htm 100660 - Disclosure - Income Taxes - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetail Income Taxes - Additional Information (Detail) Details 67 false false R68.htm 100670 - Disclosure - Income Taxes - Schedule of Reconciliation of U.S Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfUSFederalStatutoryIncomeTaxRateToCompanySEffectiveIncomeTaxRateDetail Income Taxes - Schedule of Reconciliation of U.S Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate (Detail) Details 68 false false R69.htm 100680 - Disclosure - Income Taxes - Schedule of Net Deferred Tax Assets (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxesScheduleOfNetDeferredTaxAssetsDetail Income Taxes - Schedule of Net Deferred Tax Assets (Detail) Details 69 false false R70.htm 100690 - Disclosure - Income Taxes - Summary of Changes In Valuation Allowance for Deferred Tax Assets (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureIncomeTaxesSummaryOfChangesInValuationAllowanceForDeferredTaxAssetsDetail Income Taxes - Summary of Changes In Valuation Allowance for Deferred Tax Assets (Detail) Details 70 false false R71.htm 100700 - Disclosure - Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSelectedQuarterlyFinancialDataUnauditedSummaryOfQuarterlyFinancialInformationDetail Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Detail) Details http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSelectedQuarterlyFinancialDataUnauditedTables 71 false false R72.htm 100710 - Disclosure - Related Party Transactions - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureRelatedPartyTransactionsAdditionalInformationDetail Related Party Transactions - Additional Information (Detail) Details 72 false false R73.htm 100720 - Disclosure - Subsequent Events - Additional Information (Detail) Sheet http://serestherapeutics.com/20151231/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail Subsequent Events - Additional Information (Detail) Details 73 false false All Reports Book All Reports mcrb-20151231.xml mcrb-20151231.xsd mcrb-20151231_cal.xml mcrb-20151231_def.xml mcrb-20151231_lab.xml mcrb-20151231_pre.xml true true