<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>163</ContextCount>
  <ElementCount>202</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>44</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Condensed Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/StatementCondensedBalanceSheets</Role>
      <ShortName>Condensed Balance Sheets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Condensed Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/StatementCondensedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Balance Sheets (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Condensed Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/StatementCondensedStatementsOfOperations</Role>
      <ShortName>Condensed Statements of Operations</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Condensed Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/StatementCondensedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>Condensed Statements of Comprehensive Income (Loss)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Condensed Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/StatementCondensedStatementsOfCashFlows</Role>
      <ShortName>Condensed Statements of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Disclosure - Organization</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureOrganization</Role>
      <ShortName>Organization</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureFinancialInstruments</Role>
      <ShortName>Financial Instruments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Derivative Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureDerivativeInstruments</Role>
      <ShortName>Derivative Instruments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Balance Sheet Components</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureBalanceSheetComponents</Role>
      <ShortName>Balance Sheet Components</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Collaboration and License Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureCollaborationAndLicenseAgreements</Role>
      <ShortName>Collaboration and License Agreements</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Restructuring Charge</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureRestructuringCharge</Role>
      <ShortName>Restructuring Charge</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureStockBasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Net Income (Loss) per Share Attributable to Common Stockholders</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureNetIncomeLossPerShareAttributableToCommonStockholders</Role>
      <ShortName>Net Income (Loss) per Share Attributable to Common Stockholders</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureFinancialInstrumentsTables</Role>
      <ShortName>Financial Instruments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Balance Sheet Components (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureBalanceSheetComponentsTables</Role>
      <ShortName>Balance Sheet Components (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Collaboration and License Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureCollaborationAndLicenseAgreementsTables</Role>
      <ShortName>Collaboration and License Agreements (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureStockBasedCompensationTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Net Income (Loss) per Share Attributable to Common Stockholders (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureNetIncomeLossPerShareAttributableToCommonStockholdersTables</Role>
      <ShortName>Net Income (Loss) per Share Attributable to Common Stockholders (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Organization - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureOrganizationAdditionalInformationDetail</Role>
      <ShortName>Organization - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Revenue Accounted for 10% or More of Total Revenues (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureRevenueAccountedFor10OrMoreOfTotalRevenuesDetail</Role>
      <ShortName>Revenue Accounted for 10% or More of Total Revenues (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Summary of Financial Assets, and Liabilities, Allocated into Level 1, Level 2, and Level 3 Measured on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfFinancialAssetsAndLiabilitiesAllocatedIntoLevel1Level2AndLevel3MeasuredOnRecurringBasisDetail</Role>
      <ShortName>Summary of Financial Assets, and Liabilities, Allocated into Level 1, Level 2, and Level 3 Measured on Recurring Basis (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Summary of Changes in Estimated Fair Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfChangesInEstimatedFairValueDetail</Role>
      <ShortName>Summary of Changes in Estimated Fair Value (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Estimated Fair Value of Convertible Preferred Stock Warrant determined Using Black-Sholes Option Pricing Model (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureEstimatedFairValueOfConvertiblePreferredStockWarrantDeterminedUsingBlackSholesOptionPricingModelDetail</Role>
      <ShortName>Estimated Fair Value of Convertible Preferred Stock Warrant determined Using Black-Sholes Option Pricing Model (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Cash Equivalents and Investments Classified as Available-for-sale Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureCashEquivalentsAndInvestmentsClassifiedAsAvailableForSaleSecuritiesDetail</Role>
      <ShortName>Cash Equivalents and Investments Classified as Available-for-sale Securities (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Financial Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail</Role>
      <ShortName>Financial Instruments - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Derivative Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureDerivativeInstrumentsAdditionalInformationDetail</Role>
      <ShortName>Derivative Instruments - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Accrued Expenses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureAccruedExpensesDetail</Role>
      <ShortName>Accrued Expenses (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Summary of Revenue from Collaboration and License Agreements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfRevenueFromCollaborationAndLicenseAgreementsDetail</Role>
      <ShortName>Summary of Revenue from Collaboration and License Agreements (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Collaboration and License Agreements - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureCollaborationAndLicenseAgreementsAdditionalInformationDetail</Role>
      <ShortName>Collaboration and License Agreements - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Restructuring Charge - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureRestructuringChargeAdditionalInformationDetail</Role>
      <ShortName>Restructuring Charge - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Fair Values of Employee Stock Options (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureFairValuesOfEmployeeStockOptionsDetail</Role>
      <ShortName>Fair Values of Employee Stock Options (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Summary of Stock Option Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSummaryOfStockOptionActivityDetail</Role>
      <ShortName>Summary of Stock Option Activity (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Classification of Stock-Based Compensation Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureClassificationOfStockBasedCompensationExpenseDetail</Role>
      <ShortName>Classification of Stock-Based Compensation Expense (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Stock-Based Compensation - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureStockBasedCompensationAdditionalInformationDetail</Role>
      <ShortName>Stock-Based Compensation - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Outstanding Shares of Common Stock Excluded from Computation of Diluted Net Loss per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureOutstandingSharesOfCommonStockExcludedFromComputationOfDilutedNetLossPerShareDetail</Role>
      <ShortName>Outstanding Shares of Common Stock Excluded from Computation of Diluted Net Loss per Share (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100440 - Disclosure - Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureComputationOfBasicAndDilutedNetLossPerShareAttributableToCommonStockholdersDetail</Role>
      <ShortName>Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.portola.com/20130930/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>Subsequent Events - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element ptla_ReductionToResearchAndDevelopmentExpense had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_ConcentrationRiskPercentage1 had a mix of decimals attribute values: 0 2.</Log>
    <Log type="Info">Element us-gaap_DeferredOfferingCosts had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_DeferredRevenue had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_DeferredRevenueRevenueRecognized had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_FairValueAssumptionsExpectedVolatilityRate had a mix of decimals attribute values: 0 2.</Log>
    <Log type="Info">Element us-gaap_OtherDeferredCostsNet had a mix of decimals attribute values: -6 -5.</Log>
    <Log type="Info">Element us-gaap_ResearchAndDevelopmentExpense had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">'Monetary' elements on report '100260 - Disclosure - Organization - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '100340 - Disclosure - Derivative Instruments - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '100370 - Disclosure - Collaboration and License Agreements - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '100450 - Disclosure - Subsequent Events - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 100010 - Statement - Condensed Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Sep. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 100020 - Statement - Condensed Balance Sheets (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 100030 - Statement - Condensed Statements of Operations</Log>
    <Log type="Info">Process Flow-Through: 100040 - Statement - Condensed Statements of Comprehensive Income (Loss)</Log>
    <Log type="Info">Process Flow-Through: 100050 - Statement - Condensed Statements of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>ptla-20130930.xml</File>
    <File>ptla-20130930.xsd</File>
    <File>ptla-20130930_cal.xml</File>
    <File>ptla-20130930_def.xml</File>
    <File>ptla-20130930_lab.xml</File>
    <File>ptla-20130930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
