3.22.2 html 113 166 1 false 33 0 false 4 false false R1.htm 00090 - Document - Cover Page Sheet http://gbio.com/role/DocumentCoverPage Cover Page Cover 1 false false R2.htm 00100 - Statement - Condensed Consolidated Balance Sheets Sheet http://gbio.com/role/StatementCondensedConsolidatedBalanceSheets Condensed Consolidated Balance Sheets Statements 2 false false R3.htm 00105 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://gbio.com/role/StatementCondensedConsolidatedBalanceSheetsParenthetical Condensed Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 00200 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss Sheet http://gbio.com/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLoss Condensed Consolidated Statements of Operations and Comprehensive Loss Statements 4 false false R5.htm 00300 - Statement - Condensed Consolidated Statements of Stockholders' Equity Sheet http://gbio.com/role/StatementCondensedConsolidatedStatementsOfStockholdersEquity Condensed Consolidated Statements of Stockholders' Equity Statements 5 false false R6.htm 00305 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) Sheet http://gbio.com/role/StatementCondensedConsolidatedStatementsOfStockholdersEquityParenthetical Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) Statements 6 false false R7.htm 00400 - Statement - Condensed Consolidated Statements of Cash Flows Sheet http://gbio.com/role/StatementCondensedConsolidatedStatementsOfCashFlows Condensed Consolidated Statements of Cash Flows Statements 7 false false R8.htm 10101 - Disclosure - Nature of the Business and Basis of Presentation Sheet http://gbio.com/role/DisclosureNatureOfBusinessAndBasisOfPresentation Nature of the Business and Basis of Presentation Notes 8 false false R9.htm 10201 - Disclosure - Summary of Significant Accounting Policies Sheet http://gbio.com/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 9 false false R10.htm 10301 - Disclosure - Marketable Securities And Fair Value Measurements Sheet http://gbio.com/role/DisclosureMarketableSecuritiesAndFairValueMeasurements Marketable Securities And Fair Value Measurements Notes 10 false false R11.htm 10401 - Disclosure - Property and equipment, net Sheet http://gbio.com/role/DisclosurePropertyAndEquipmentNet Property and equipment, net Notes 11 false false R12.htm 10501 - Disclosure - Accrued Expenses Sheet http://gbio.com/role/DisclosureAccruedExpenses Accrued Expenses Notes 12 false false R13.htm 10601 - Disclosure - Equity Sheet http://gbio.com/role/DisclosureEquity Equity Notes 13 false false R14.htm 10701 - Disclosure - Stock-Based Compensation Sheet http://gbio.com/role/DisclosureStockBasedCompensation Stock-Based Compensation Notes 14 false false R15.htm 10801 - Disclosure - Commitments and Contingencies Sheet http://gbio.com/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 15 false false R16.htm 10901 - Disclosure - Net Loss per Share Sheet http://gbio.com/role/DisclosureNetLossPerShare Net Loss per Share Notes 16 false false R17.htm 20202 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://gbio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://gbio.com/role/DisclosureSummaryOfSignificantAccountingPolicies 17 false false R18.htm 30303 - Disclosure - Marketable Securities And Fair Value Measurements (Tables) Sheet http://gbio.com/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsTables Marketable Securities And Fair Value Measurements (Tables) Tables http://gbio.com/role/DisclosureMarketableSecuritiesAndFairValueMeasurements 18 false false R19.htm 30403 - Disclosure - Property and equipment, net (Tables) Sheet http://gbio.com/role/DisclosurePropertyAndEquipmentNetTables Property and equipment, net (Tables) Tables http://gbio.com/role/DisclosurePropertyAndEquipmentNet 19 false false R20.htm 30503 - Disclosure - Accrued Expenses (Tables) Sheet http://gbio.com/role/DisclosureAccruedExpensesTables Accrued Expenses (Tables) Tables http://gbio.com/role/DisclosureAccruedExpenses 20 false false R21.htm 30703 - Disclosure - Stock-Based Compensation (Tables) Sheet http://gbio.com/role/DisclosureStockBasedCompensationTables Stock-Based Compensation (Tables) Tables http://gbio.com/role/DisclosureStockBasedCompensation 21 false false R22.htm 30903 - Disclosure - Net Loss per Share (Tables) Sheet http://gbio.com/role/DisclosureNetLossPerShareTables Net Loss per Share (Tables) Tables http://gbio.com/role/DisclosureNetLossPerShare 22 false false R23.htm 40101 - Disclosure - Nature of the Business and Basis of Presentation - Additional information (Detail) Sheet http://gbio.com/role/DisclosureNatureOfBusinessAndBasisOfPresentationAdditionalInformationDetail Nature of the Business and Basis of Presentation - Additional information (Detail) Details 23 false false R24.htm 40301 - Disclosure - Marketable Securities And Fair Value Measurements - Summary of marketable securities (Detail) Sheet http://gbio.com/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsSummaryOfMarketableSecuritiesDetail Marketable Securities And Fair Value Measurements - Summary of marketable securities (Detail) Details 24 false false R25.htm 40302 - Disclosure - Marketable Securities And Fair Value Measurements - Summary of assets measured at fair value on a recurring basis (Detail) Sheet http://gbio.com/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsSummaryOfAssetsMeasuredAtFairValueOnRecurringBasisDetail Marketable Securities And Fair Value Measurements - Summary of assets measured at fair value on a recurring basis (Detail) Details 25 false false R26.htm 40401 - Disclosure - Property and equipment, net - Summary of Property and equipment, net (Detail) Sheet http://gbio.com/role/DisclosurePropertyAndEquipmentNetSummaryOfPropertyAndEquipmentNetDetail Property and equipment, net - Summary of Property and equipment, net (Detail) Details 26 false false R27.htm 40402 - Disclosure - Property and equipment, net - Additional Information (Detail) Sheet http://gbio.com/role/DisclosurePropertyAndEquipmentNetAdditionalInformationDetail Property and equipment, net - Additional Information (Detail) Details 27 false false R28.htm 40501 - Disclosure - Accrued Expenses - Summary of Accrued expenses (Detail) Sheet http://gbio.com/role/DisclosureAccruedExpensesSummaryOfAccruedExpensesDetail Accrued Expenses - Summary of Accrued expenses (Detail) Details 28 false false R29.htm 40601 - Disclosure - Equity - Additional Information (Detail) Sheet http://gbio.com/role/DisclosureEquityAdditionalInformationDetail Equity - Additional Information (Detail) Details 29 false false R30.htm 40701 - Disclosure - Stock-Based Compensation - Additional Information (Detail) Sheet http://gbio.com/role/DisclosureStockBasedCompensationAdditionalInformationDetail Stock-Based Compensation - Additional Information (Detail) Details 30 false false R31.htm 40702 - Disclosure - Stock-Based Compensation - Summary of Stock-Based Compensation Expense was Classified in the Statements of Operations and Comprehensive Loss (Detail) Sheet http://gbio.com/role/DisclosureStockBasedCompensationSummaryOfStockBasedCompensationExpenseWasClassifiedInStatementsOfOperationsAndComprehensiveLossDetail Stock-Based Compensation - Summary of Stock-Based Compensation Expense was Classified in the Statements of Operations and Comprehensive Loss (Detail) Details 31 false false R32.htm 40801 - Disclosure - Commitments and Contingencies - Additional Information (Detail) Sheet http://gbio.com/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail Commitments and Contingencies - Additional Information (Detail) Details 32 false false R33.htm 40901 - Disclosure - Net Loss per Share - Summary of Potential Dilutive Securities, Presented Based on Amounts Outstanding (Detail) Sheet http://gbio.com/role/DisclosureNetLossPerShareSummaryOfPotentialDilutiveSecuritiesPresentedBasedOnAmountsOutstandingDetail Net Loss per Share - Summary of Potential Dilutive Securities, Presented Based on Amounts Outstanding (Detail) Details 33 false false All Reports Book All Reports gbio-20220630x10q.htm gbio-20220630.xsd gbio-20220630_cal.xml gbio-20220630_def.xml gbio-20220630_lab.xml gbio-20220630_pre.xml gbio-20220630xex10d1.htm gbio-20220630xex31d1.htm gbio-20220630xex31d2.htm gbio-20220630xex32d1.htm gbio-20220630xex32d2.htm http://fasb.org/us-gaap/2021-01-31 http://xbrl.sec.gov/dei/2021q4 true true