3.3.1.900 html 286 381 1 false 101 0 false 11 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://cytomx.com/20151231/taxonomy/role/DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - BALANCE SHEETS Sheet http://cytomx.com/20151231/taxonomy/role/StatementBALANCESHEETS BALANCE SHEETS Statements 2 false false R3.htm 100020 - Statement - BALANCE SHEETS (Parenthetical) Sheet http://cytomx.com/20151231/taxonomy/role/StatementBALANCESHEETSParenthetical BALANCE SHEETS (Parenthetical) Statements 3 false false R4.htm 100030 - Statement - STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS Sheet http://cytomx.com/20151231/taxonomy/role/StatementSTATEMENTSOFOPERATIONSANDCOMPREHENSIVELOSS STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS Statements 4 false false R5.htm 100040 - Statement - STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) Sheet http://cytomx.com/20151231/taxonomy/role/StatementSTATEMENTSOFREDEEMABLECONVERTIBLEPREFERREDSTOCKCONVERTIBLEPREFERREDSTOCKANDSTOCKHOLDERSEQUITYDEFICIT STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) Statements 5 false false R6.htm 100050 - Statement - STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) Sheet http://cytomx.com/20151231/taxonomy/role/StatementSTATEMENTSOFREDEEMABLECONVERTIBLEPREFERREDSTOCKCONVERTIBLEPREFERREDSTOCKANDSTOCKHOLDERSEQUITYDEFICITParenthetical STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) Statements 6 false false R7.htm 100060 - Statement - STATEMENTS OF CASH FLOWS Sheet http://cytomx.com/20151231/taxonomy/role/StatementSTATEMENTSOFCASHFLOWS STATEMENTS OF CASH FLOWS Statements 7 false false R8.htm 100070 - Disclosure - Description of the Business Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureDescriptionOfBusiness Description of the Business Notes 8 false false R9.htm 100080 - Disclosure - Liquidity Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLiquidity Liquidity Notes 9 false false R10.htm 100090 - Disclosure - Summary of Significant Accounting Policies Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 10 false false R11.htm 100100 - Disclosure - Fair Value Measurements and Short-term Investments Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestments Fair Value Measurements and Short-term Investments Notes 11 false false R12.htm 100110 - Disclosure - Property and Equipment Sheet http://cytomx.com/20151231/taxonomy/role/DisclosurePropertyAndEquipment Property and Equipment Notes 12 false false R13.htm 100120 - Disclosure - Goodwill and Intangible Assets Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureGoodwillAndIntangibleAssets Goodwill and Intangible Assets Notes 13 false false R14.htm 100130 - Disclosure - Accrued Liabilities Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureAccruedLiabilities Accrued Liabilities Notes 14 false false R15.htm 100140 - Disclosure - Research and Collaboration Agreements Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureResearchAndCollaborationAgreements Research and Collaboration Agreements Notes 15 false false R16.htm 100150 - Disclosure - License Agreement Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLicenseAgreement License Agreement Notes 16 false false R17.htm 100160 - Disclosure - Long-term Debt Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLongTermDebt Long-term Debt Notes 17 false false R18.htm 100170 - Disclosure - Commitments and Contingencies Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 18 false false R19.htm 100180 - Disclosure - Convertible Preferred Stock Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStock Convertible Preferred Stock Notes 19 false false R20.htm 100190 - Disclosure - Common Stock Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommonStock Common Stock Notes 20 false false R21.htm 100200 - Disclosure - Stock Option Plans Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockOptionPlans Stock Option Plans Notes 21 false false R22.htm 100210 - Disclosure - Stock Based Compensation Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockBasedCompensation Stock Based Compensation Notes 22 false false R23.htm 100220 - Disclosure - Related Party Transactions Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureRelatedPartyTransactions Related Party Transactions Notes 23 false false R24.htm 100230 - Disclosure - Income Taxes Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxes Income Taxes Notes 24 false false R25.htm 100240 - Disclosure - Defined Contribution Plan Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureDefinedContributionPlan Defined Contribution Plan Notes 25 false false R26.htm 100250 - Disclosure - Net Loss Per Share Attributable to Common Stockholders Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholders Net Loss Per Share Attributable to Common Stockholders Notes 26 false false R27.htm 100260 - Disclosure - Supplementary Data - Quarterly Financial Data (Unaudited) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSupplementaryDataQuarterlyFinancialDataUnaudited Supplementary Data - Quarterly Financial Data (Unaudited) Notes 27 false false R28.htm 100270 - Disclosure - Subsequent Events Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSubsequentEvents Subsequent Events Notes 28 false false R29.htm 100280 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 29 false false R30.htm 100290 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 30 false false R31.htm 100300 - Disclosure - Fair Value Measurements and Short-term Investments (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestmentsTables Fair Value Measurements and Short-term Investments (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestments 31 false false R32.htm 100310 - Disclosure - Property and Equipment (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentTables Property and Equipment (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosurePropertyAndEquipment 32 false false R33.htm 100320 - Disclosure - Goodwill and Intangible Assets (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsTables Goodwill and Intangible Assets (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureGoodwillAndIntangibleAssets 33 false false R34.htm 100330 - Disclosure - Accrued Liabilities (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureAccruedLiabilitiesTables Accrued Liabilities (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureAccruedLiabilities 34 false false R35.htm 100340 - Disclosure - License Agreement (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLicenseAgreementTables License Agreement (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureLicenseAgreement 35 false false R36.htm 100350 - Disclosure - Commitments and Contingencies (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingenciesTables Commitments and Contingencies (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingencies 36 false false R37.htm 100360 - Disclosure - Convertible Preferred Stock (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStockTables Convertible Preferred Stock (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStock 37 false false R38.htm 100370 - Disclosure - Common Stock (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommonStockTables Common Stock (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureCommonStock 38 false false R39.htm 100380 - Disclosure - Stock Option Plans (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockOptionPlansTables Stock Option Plans (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureStockOptionPlans 39 false false R40.htm 100390 - Disclosure - Stock Based Compensation (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockBasedCompensationTables Stock Based Compensation (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureStockBasedCompensation 40 false false R41.htm 100400 - Disclosure - Income Taxes (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxesTables Income Taxes (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxes 41 false false R42.htm 100410 - Disclosure - Net Loss Per Share Attributable to Common Stockholders (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersTables Net Loss Per Share Attributable to Common Stockholders (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholders 42 false false R43.htm 100420 - Disclosure - Supplementary Data - Quarterly Financial Data (Unaudited) (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSupplementaryDataQuarterlyFinancialDataUnauditedTables Supplementary Data - Quarterly Financial Data (Unaudited) (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureSupplementaryDataQuarterlyFinancialDataUnaudited 43 false false R44.htm 100430 - Disclosure - Subsequent Events (Tables) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSubsequentEventsTables Subsequent Events (Tables) Tables http://cytomx.com/20151231/taxonomy/role/DisclosureSubsequentEvents 44 false false R45.htm 100440 - Disclosure - Description of the Business - Additional Information (Detail) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureDescriptionOfBusinessAdditionalInformationDetail Description of the Business - Additional Information (Detail) Details 45 false false R46.htm 100450 - Disclosure - Liquidity - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLiquidityAdditionalInformationDetails Liquidity - Additional Information (Details) Details 46 false false R47.htm 100460 - Disclosure - Summary of Significant Accounting Policies - Schedule of Customers Represent 10% or More of Total Revenue During Each Period Presented or Net Accounts Receivable Balance (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfCustomersRepresent10OrMoreOfTotalRevenueDuringEachPeriodPresentedOrNetAccountsReceivableBalanceDetails Summary of Significant Accounting Policies - Schedule of Customers Represent 10% or More of Total Revenue During Each Period Presented or Net Accounts Receivable Balance (Details) Details 47 false false R48.htm 100470 - Disclosure - Summary of Significant Accounting Policies - Schedule of Customers Represent 10% or More of Total Revenue or Net Accounts Receivable Balance (Details) (Parenthetical) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfCustomersRepresent10OrMoreOfTotalRevenueOrNetAccountsReceivableBalanceDetailsParenthetical Summary of Significant Accounting Policies - Schedule of Customers Represent 10% or More of Total Revenue or Net Accounts Receivable Balance (Details) (Parenthetical) Details 48 false false R49.htm 100480 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails Summary of Significant Accounting Policies - Additional Information (Details) Details 49 false false R50.htm 100490 - Disclosure - Summary of Significant Accounting Policies - Schedule of Useful Lives of Property and Equipment (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfUsefulLivesOfPropertyAndEquipmentDetails Summary of Significant Accounting Policies - Schedule of Useful Lives of Property and Equipment (Details) Details 50 false false R51.htm 100500 - Disclosure - Fair Value Measurements and Short-term Investments - Schedule of Financial Assets and Liabilities Subject to Fair Value Measurements on a Recurring Basis (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestmentsScheduleOfFinancialAssetsAndLiabilitiesSubjectToFairValueMeasurementsOnRecurringBasisDetails Fair Value Measurements and Short-term Investments - Schedule of Financial Assets and Liabilities Subject to Fair Value Measurements on a Recurring Basis (Details) Details 51 false false R52.htm 100510 - Disclosure - Fair Value Measurements and Short-term Investments - Summary of Changes in the Fair Value of Level 3 Liabilities (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestmentsSummaryOfChangesInFairValueOfLevel3LiabilitiesDetails Fair Value Measurements and Short-term Investments - Summary of Changes in the Fair Value of Level 3 Liabilities (Details) Details 52 false false R53.htm 100520 - Disclosure - Fair Value Measurements and Short-term Investment - Summary of Gross Unrealized Gains on the Company Short-term Investments (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestmentSummaryOfGrossUnrealizedGainsOnCompanyShortTermInvestmentsDetails Fair Value Measurements and Short-term Investment - Summary of Gross Unrealized Gains on the Company Short-term Investments (Details) Details 53 false false R54.htm 100530 - Disclosure - Fair Value Measurements and Short-term Investments - Schedule of Contractual Maturities of Securities Classified as Available-for-sale (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureFairValueMeasurementsAndShortTermInvestmentsScheduleOfContractualMaturitiesOfSecuritiesClassifiedAsAvailableForSaleDetails Fair Value Measurements and Short-term Investments - Schedule of Contractual Maturities of Securities Classified as Available-for-sale (Details) Details 54 false false R55.htm 100540 - Disclosure - Property and Equipment - Summary of Property and Equipment, Net (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentSummaryOfPropertyAndEquipmentNetDetails Property and Equipment - Summary of Property and Equipment, Net (Details) Details 55 false false R56.htm 100550 - Disclosure - Property and Equipment - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosurePropertyAndEquipmentAdditionalInformationDetails Property and Equipment - Additional Information (Details) Details 56 false false R57.htm 100560 - Disclosure - Goodwill and Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsScheduleOfGoodwillAndIntangibleAssetsDetails Goodwill and Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) Details 57 false false R58.htm 100570 - Disclosure - Accrued Liabilities - Summary of Accrued Liabilities (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureAccruedLiabilitiesSummaryOfAccruedLiabilitiesDetails Accrued Liabilities - Summary of Accrued Liabilities (Details) Details 58 false false R59.htm 100580 - Disclosure - Research and Collaboration Agreements - Pfizer Inc - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureResearchAndCollaborationAgreementsPfizerIncAdditionalInformationDetails Research and Collaboration Agreements - Pfizer Inc - Additional Information (Details) Details 59 false false R60.htm 100590 - Disclosure - Research and Collaboration Agreements - ImmunoGen, Inc - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureResearchAndCollaborationAgreementsImmunogenIncAdditionalInformationDetails Research and Collaboration Agreements - ImmunoGen, Inc - Additional Information (Details) Details 60 false false R61.htm 100600 - Disclosure - Research and Collaboration Agreements - Bristol-Myers Squibb Company - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureResearchAndCollaborationAgreementsBristolMyersSquibbCompanyAdditionalInformationDetails Research and Collaboration Agreements - Bristol-Myers Squibb Company - Additional Information (Details) Details 61 false false R62.htm 100610 - Disclosure - Research and Collaboration Agreements - MD Anderson - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureResearchAndCollaborationAgreementsMDAndersonAdditionalInformationDetails Research and Collaboration Agreements - MD Anderson - Additional Information (Details) Details 62 false false R63.htm 100620 - Disclosure - License Agreement - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLicenseAgreementAdditionalInformationDetails License Agreement - Additional Information (Details) Details 63 false false R64.htm 100630 - Disclosure - License Agreement - Schedule of Future Minimum Royalty Obligations Due Under Terms of Certain Exclusive Licensed Patent Rights (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLicenseAgreementScheduleOfFutureMinimumRoyaltyObligationsDueUnderTermsOfCertainExclusiveLicensedPatentRightsDetails License Agreement - Schedule of Future Minimum Royalty Obligations Due Under Terms of Certain Exclusive Licensed Patent Rights (Details) Details 64 false false R65.htm 100640 - Disclosure - Long-term Debt - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureLongTermDebtAdditionalInformationDetails Long-term Debt - Additional Information (Details) Details 65 false false R66.htm 100650 - Disclosure - Commitments and Contingencies - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetails Commitments and Contingencies - Additional Information (Details) Details 66 false false R67.htm 100660 - Disclosure - Commitments and Contingencies - Schedule of Future Minimum Lease Payments (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommitmentsAndContingenciesScheduleOfFutureMinimumLeasePaymentsDetails Commitments and Contingencies - Schedule of Future Minimum Lease Payments (Details) Details 67 false false R68.htm 100670 - Disclosure - Convertible Preferred Stock - Additional information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStockAdditionalInformationDetails Convertible Preferred Stock - Additional information (Details) Details 68 false false R69.htm 100680 - Disclosure - Convertible Preferred Stock - Summary of Convertible Preferred Stock (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureConvertiblePreferredStockSummaryOfConvertiblePreferredStockDetails Convertible Preferred Stock - Summary of Convertible Preferred Stock (Details) Details 69 false false R70.htm 100690 - Disclosure - Common Stock - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommonStockAdditionalInformationDetails Common Stock - Additional Information (Details) Details 70 false false R71.htm 100700 - Disclosure - Common Stock - Reserved Shares of Common Stock Issuance on Converted Basis (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureCommonStockReservedSharesOfCommonStockIssuanceOnConvertedBasisDetails Common Stock - Reserved Shares of Common Stock Issuance on Converted Basis (Details) Details 71 false false R72.htm 100710 - Disclosure - Stock Option Plans - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockOptionPlansAdditionalInformationDetails Stock Option Plans - Additional Information (Details) Details 72 false false R73.htm 100720 - Disclosure - Stock Option Plans - Schedule of Activity Under Company's Stock Option Plans (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockOptionPlansScheduleOfActivityUnderCompanySStockOptionPlansDetails Stock Option Plans - Schedule of Activity Under Company's Stock Option Plans (Details) Details 73 false false R74.htm 100730 - Disclosure - Stock Option Plans - Summary of Stock Options Outstanding and Exercisable by Exercise Price (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockOptionPlansSummaryOfStockOptionsOutstandingAndExercisableByExercisePriceDetails Stock Option Plans - Summary of Stock Options Outstanding and Exercisable by Exercise Price (Details) Details 74 false false R75.htm 100740 - Disclosure - Stock Based Compensation - Total Stock-based Compensation Recorded Related to Option Granted to Employees and Nonemployees (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockBasedCompensationTotalStockBasedCompensationRecordedRelatedToOptionGrantedToEmployeesAndNonemployeesDetails Stock Based Compensation - Total Stock-based Compensation Recorded Related to Option Granted to Employees and Nonemployees (Details) Details 75 false false R76.htm 100750 - Disclosure - Stock Based Compensation - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockBasedCompensationAdditionalInformationDetails Stock Based Compensation - Additional Information (Details) Details 76 false false R77.htm 100760 - Disclosure - Stock Based Compensation-Schedule of Estimated Fair Value of Employee Stock Options Using Black-Scholes Valuation Model (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureStockBasedCompensationScheduleOfEstimatedFairValueOfEmployeeStockOptionsUsingBlackScholesValuationModelDetails Stock Based Compensation-Schedule of Estimated Fair Value of Employee Stock Options Using Black-Scholes Valuation Model (Details) Details 77 false false R78.htm 100770 - Disclosure - Related Party Transactions - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureRelatedPartyTransactionsAdditionalInformationDetails Related Party Transactions - Additional Information (Details) Details 78 false false R79.htm 100780 - Disclosure - Income Taxes - Schedule of Components of Provision (Benefit) for Income Taxes (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxesScheduleOfComponentsOfProvisionBenefitForIncomeTaxesDetails Income Taxes - Schedule of Components of Provision (Benefit) for Income Taxes (Details) Details 79 false false R80.htm 100790 - Disclosure - Income Taxes - Schedule of Effective Tax Rate Reconciliation (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxesScheduleOfEffectiveTaxRateReconciliationDetails Income Taxes - Schedule of Effective Tax Rate Reconciliation (Details) Details 80 false false R81.htm 100800 - Disclosure - Income Taxes - Schedule of Deferred Income Tax Liabilities (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxesScheduleOfDeferredIncomeTaxLiabilitiesDetails Income Taxes - Schedule of Deferred Income Tax Liabilities (Details) Details 81 false false R82.htm 100810 - Disclosure - Income Taxes - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetails Income Taxes - Additional Information (Details) Details 82 false false R83.htm 100820 - Disclosure - Income Taxes- Schedule of Reconciliation of Unrecognized Tax Benefits (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfUnrecognizedTaxBenefitsDetails Income Taxes- Schedule of Reconciliation of Unrecognized Tax Benefits (Details) Details 83 false false R84.htm 100830 - Disclosure - Defined Contribution Plan - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureDefinedContributionPlanAdditionalInformationDetails Defined Contribution Plan - Additional Information (Details) Details 84 false false R85.htm 100840 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersSummaryOfPotentiallyDilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerShareDetails Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) Details 85 false false R86.htm 100850 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Loss Per Share (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureNetLossPerShareAttributableToCommonStockholdersReconciliationOfNumeratorAndDenominatorUsedInCalculationOfBasicAndDilutedNetLossPerShareDetails Net Loss Per Share Attributable to Common Stockholders - Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Loss Per Share (Details) Details 86 false false R87.htm 100860 - Disclosure - Supplementary Data - Quarterly Financial Data (Unaudited) - Unaudited Financial Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSupplementaryDataQuarterlyFinancialDataUnauditedUnauditedFinancialInformationDetails Supplementary Data - Quarterly Financial Data (Unaudited) - Unaudited Financial Information (Details) Details http://cytomx.com/20151231/taxonomy/role/DisclosureSupplementaryDataQuarterlyFinancialDataUnauditedTables 87 false false R88.htm 100870 - Disclosure - Subsequent Events - Additional Information (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails Subsequent Events - Additional Information (Details) Details 88 false false R89.htm 100880 - Disclosure - Subsequent Events - Schedule of Future Minimum Lease Payments (Details) Sheet http://cytomx.com/20151231/taxonomy/role/DisclosureSubsequentEventsScheduleOfFutureMinimumLeasePaymentsDetails Subsequent Events - Schedule of Future Minimum Lease Payments (Details) Details 89 false false All Reports Book All Reports ctmx-20151231.xml ctmx-20151231.xsd ctmx-20151231_cal.xml ctmx-20151231_def.xml ctmx-20151231_lab.xml ctmx-20151231_pre.xml true true