2.4.0.8100410 - Disclosure - Stock-Based Compensation - Additional Information (Detail)truefalsefalse1false falsefalseC_0001269021_20130630http://www.sec.gov/CIK0001269021instant2013-06-30T00:00:000001-01-01T00:00:00U_sharesStandardhttp://www.xbrl.org/2003/instanceshares01true 3us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]2false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse334070334070falsefalsefalsexbrli:sharesItemTypesharesThe maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Number of common stock shares reserved for issuance under the 2003 Equity Incentive PlanfalseStock-Based Compensation - Additional Information (Detail)UnKnownNoRoundingUnKnownUnKnowntruefalsefalseSheethttp://www.portola.com/20130630/taxonomy/role/DisclosureStockBasedCompensationAdditionalInformationDetail12