2.4.0.8100390 - Disclosure - Summary of Stock Option Activity (Detail)truefalsefalse1false USDfalsefalse$C_0001269021_20130101_20130630http://www.sec.gov/CIK0001269021duration2013-01-01T00:00:002013-06-30T00:00:00U_sharesStandardhttp://www.xbrl.org/2003/instanceshares0U_iso4217USD_sharesDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instanceshares0USDUSD$1true 4ptla_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantAbstractptla_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share Available for Grant2false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantus-gaap_truenainstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse593011593011falsefalsefalsexbrli:sharesItemTypesharesThe difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Balance at December 31, 20123false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorizedus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse150000150000falsefalsefalsexbrli:sharesItemTypesharesNumber of additional shares authorized for issuance under an established share-based compensation plan.No definition available.false1Options authorized4false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrossus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-560854-560854falsefalsefalsexbrli:sharesItemTypesharesGross number of share options (or share units) granted during the period.No definition available.false1Options granted5false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriodus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse151913151913falsefalsefalsexbrli:sharesItemTypesharesThe number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(f) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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