<?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>HtmlAndXml</ReportFormat>
  <ContextCount>124</ContextCount>
  <ElementCount>246</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>51</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>101 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DocumentDocumentandEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <XmlFileName>R1.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>103 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/StatementOfFinancialPositionClassified</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <XmlFileName>R2.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>104 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/StatementOfFinancialPositionClassifiedParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <XmlFileName>R3.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>105 - Statement - Condensed Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/StatementOfIncome</Role>
      <ShortName>Condensed Consolidated Statements of Operations</ShortName>
      <XmlFileName>R4.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>106 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/StatementOfOtherComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Loss)</ShortName>
      <XmlFileName>R5.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>107 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/StatementOfOtherComprehensiveIncomeParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)</ShortName>
      <XmlFileName>R6.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>108 - Statement - Condensed Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/StatementOfCashFlowsIndirect</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows</ShortName>
      <XmlFileName>R7.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>109 - Disclosure - Business</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock</Role>
      <ShortName>Business</ShortName>
      <XmlFileName>R8.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>110 - Disclosure - Restatement of Previously Issued Financial Statements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsAccountingChangesAndErrorCorrectionsTextBlock</Role>
      <ShortName>Restatement of Previously Issued Financial Statements</ShortName>
      <XmlFileName>R9.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>111 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsBasisOfPresentationAndSignificantAccountingPoliciesTextBlock</Role>
      <ShortName>Basis of Presentation</ShortName>
      <XmlFileName>R10.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>112 - Disclosure - Balance Sheet Details</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsSupplementalBalanceSheetDisclosuresTextBlock</Role>
      <ShortName>Balance Sheet Details</ShortName>
      <XmlFileName>R11.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>113 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsDebtDisclosureTextBlock</Role>
      <ShortName>Debt</ShortName>
      <XmlFileName>R12.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>114 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsIncomeTaxDisclosureTextBlock</Role>
      <ShortName>Income Taxes</ShortName>
      <XmlFileName>R13.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>115 - Disclosure - Other Comprehensive Income (Loss) ("OCI")</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock</Role>
      <ShortName>Other Comprehensive Income (Loss) ("OCI")</ShortName>
      <XmlFileName>R14.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>116 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <XmlFileName>R15.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>117 - Disclosure - Pension and Post-Retirement Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsPensionAndOtherPostretirementBenefitsDisclosureTextBlock</Role>
      <ShortName>Pension and Post-Retirement Benefit Plans</ShortName>
      <XmlFileName>R16.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>118 - Disclosure - Fair Value Measurements and Derivative Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsDerivativesAndFairValueTextBlock</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments</ShortName>
      <XmlFileName>R17.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>119 - Disclosure - Segment Reporting (Restated)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlock</Role>
      <ShortName>Segment Reporting (Restated)</ShortName>
      <XmlFileName>R18.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>120 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlock</Role>
      <ShortName>Earnings Per Share</ShortName>
      <XmlFileName>R19.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>121 - Disclosure - Legal Proceedings and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsLegalMattersAndContingenciesTextBlock</Role>
      <ShortName>Legal Proceedings and Contingencies</ShortName>
      <XmlFileName>R20.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>122 - Disclosure - Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsBasisOfPresentationAndSignificantAccountingPoliciesTextBlockPolicies</Role>
      <ShortName>Basis of Presentation (Policies)</ShortName>
      <XmlFileName>R21.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>123 - Disclosure - Restatement of Previously Issued Financial Statements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsAccountingChangesAndErrorCorrectionsTextBlockTables</Role>
      <ShortName>Restatement of Previously Issued Financial Statements (Tables)</ShortName>
      <XmlFileName>R22.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>124 - Disclosure - Balance Sheet Details (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsSupplementalBalanceSheetDisclosuresTextBlockTables</Role>
      <ShortName>Balance Sheet Details (Tables)</ShortName>
      <XmlFileName>R23.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>125 - Disclosure - Other Comprehensive Income (Loss) ("OCI") (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlockTables</Role>
      <ShortName>Other Comprehensive Income (Loss) ("OCI") (Tables)</ShortName>
      <XmlFileName>R24.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>126 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlockTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
      <XmlFileName>R25.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>127 - Disclosure - Pension and Post-Retirement Benefit Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsPensionAndOtherPostretirementBenefitsDisclosureTextBlockTables</Role>
      <ShortName>Pension and Post-Retirement Benefit Plans (Tables)</ShortName>
      <XmlFileName>R26.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>128 - Disclosure - Fair Value Measurements and Derivative Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsDerivativesAndFairValueTextBlockTables</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments (Tables)</ShortName>
      <XmlFileName>R27.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>129 - Disclosure - Segment Reporting (Restated) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlockTables</Role>
      <ShortName>Segment Reporting (Restated) (Tables)</ShortName>
      <XmlFileName>R28.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>130 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlockTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <XmlFileName>R29.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>131 - Disclosure - Business - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureBusinessAdditionalInformation</Role>
      <ShortName>Business - Additional Information (Detail)</ShortName>
      <XmlFileName>R30.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>132 - Disclosure - Restatement of Previously Issued Financial Statements - Reconciliation of Sales and Cost of Sales (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureRestatementOfPreviouslyIssuedFinancialStatementsReconciliationOfSalesAndCostOfSales</Role>
      <ShortName>Restatement of Previously Issued Financial Statements - Reconciliation of Sales and Cost of Sales (Detail)</ShortName>
      <XmlFileName>R31.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>133 - Disclosure - Restatement of Previously Issued Financial Statements - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureRestatementOfPreviouslyIssuedFinancialStatementsAdditionalInformation</Role>
      <ShortName>Restatement of Previously Issued Financial Statements - Additional Information (Detail)</ShortName>
      <XmlFileName>R32.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>134 - Disclosure - Balance Sheet Details - Components of Inventory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureBalanceSheetDetailsComponentsOfInventory</Role>
      <ShortName>Balance Sheet Details - Components of Inventory (Detail)</ShortName>
      <XmlFileName>R33.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>135 - Disclosure - Balance Sheet Details - Components of Property Plant and Equipment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureBalanceSheetDetailsComponentsOfPropertyPlantAndEquipment</Role>
      <ShortName>Balance Sheet Details - Components of Property Plant and Equipment (Detail)</ShortName>
      <XmlFileName>R34.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>136 - Disclosure - Balance Sheet Details - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureBalanceSheetDetailsAdditionalInformation</Role>
      <ShortName>Balance Sheet Details - Additional Information (Detail)</ShortName>
      <XmlFileName>R35.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>137 - Disclosure - Balance Sheet Details - Components of Accrued Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureBalanceSheetDetailsComponentsOfAccruedLiabilities</Role>
      <ShortName>Balance Sheet Details - Components of Accrued Liabilities (Detail)</ShortName>
      <XmlFileName>R36.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>138 - Disclosure - Debt - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureDebtAdditionalInformation</Role>
      <ShortName>Debt - Additional Information (Detail)</ShortName>
      <XmlFileName>R37.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>139 - Disclosure - Income Taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureIncomeTaxesAdditionalInformation</Role>
      <ShortName>Income Taxes - Additional Information (Detail)</ShortName>
      <XmlFileName>R38.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>140 - Disclosure - Other Comprehensive Income (Loss) ("OCI") - Components of Accumulated Other Comprehensive Income (Loss) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureOtherComprehensiveIncomeLossOCIComponentsOfAccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>Other Comprehensive Income (Loss) ("OCI") - Components of Accumulated Other Comprehensive Income (Loss) (Detail)</ShortName>
      <XmlFileName>R39.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>141 - Disclosure - Stock-Based Compensation - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureStockBasedCompensationAdditionalInformation</Role>
      <ShortName>Stock-Based Compensation - Additional Information (Detail)</ShortName>
      <XmlFileName>R40.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>142 - Disclosure - Stock-Based Compensation - Schedule of Share Based Compensation Stock Options Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureStockBasedCompensationScheduleOfShareBasedCompensationStockOptionsActivity</Role>
      <ShortName>Stock-Based Compensation - Schedule of Share Based Compensation Stock Options Activity (Detail)</ShortName>
      <XmlFileName>R41.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>143 - Disclosure - Stock-Based Compensation - Schedule of Share Based Payment Award Stock Options Valuation Assumptions (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureStockBasedCompensationScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptions</Role>
      <ShortName>Stock-Based Compensation - Schedule of Share Based Payment Award Stock Options Valuation Assumptions (Detail)</ShortName>
      <XmlFileName>R42.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>144 - Disclosure - Stock-Based Compensation - Schedule of Share-Based Compensation, Restricted Stock Award Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureStockBasedCompensationScheduleOfShareBasedCompensationRestrictedStockAwardActivity</Role>
      <ShortName>Stock-Based Compensation - Schedule of Share-Based Compensation, Restricted Stock Award Activity (Detail)</ShortName>
      <XmlFileName>R43.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>145 - Disclosure - Stock-Based Compensation - Schedule of Employee Service Share-Based Compensation, Allocation of Recognized Period Costs (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureStockBasedCompensationScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCosts</Role>
      <ShortName>Stock-Based Compensation - Schedule of Employee Service Share-Based Compensation, Allocation of Recognized Period Costs (Detail)</ShortName>
      <XmlFileName>R44.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>146 - Disclosure - Pension and Post-Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosurePensionAndPostRetirementBenefitPlansComponentsOfNetPeriodicBenefitCost</Role>
      <ShortName>Pension and Post-Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Detail)</ShortName>
      <XmlFileName>R45.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>147 - Disclosure - Fair Value Measurements and Derivative Instruments - Fair Value of Companys Derivatives (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureFairValueMeasurementsAndDerivativeInstrumentsFairValueOfCompanysDerivatives</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments - Fair Value of Companys Derivatives (Detail)</ShortName>
      <XmlFileName>R46.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>148 - Disclosure - Fair Value Measurements and Derivative Instruments - Fair Value of Companys Derivatives (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureFairValueMeasurementsAndDerivativeInstrumentsFairValueOfCompanysDerivativesParenthetical</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments - Fair Value of Companys Derivatives (Parenthetical) (Detail)</ShortName>
      <XmlFileName>R47.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>149 - Disclosure - Fair Value Measurements and Derivative Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureFairValueMeasurementsAndDerivativeInstrumentsAdditionalInformation</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments - Additional Information (Detail)</ShortName>
      <XmlFileName>R48.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>150 - Disclosure - Fair Value Measurement and Derivative Instruments - Outstanding Future Contracts (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureFairValueMeasurementAndDerivativeInstrumentsOutstandingFutureContracts</Role>
      <ShortName>Fair Value Measurement and Derivative Instruments - Outstanding Future Contracts (Detail)</ShortName>
      <XmlFileName>R49.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>151 - Disclosure - Fair Value Measurements and Derivative Instruments - Fair Value of Company's Derivative by Contract Type (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureFairValueMeasurementsAndDerivativeInstrumentsFairValueOfCompanysDerivativeByContractType</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments - Fair Value of Company's Derivative by Contract Type (Detail)</ShortName>
      <XmlFileName>R50.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>152 - Disclosure - Fair Value Measurements and Derivative Instruments - Effect of Derivative Instruments on Company's Financial Performance (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureFairValueMeasurementsAndDerivativeInstrumentsEffectOfDerivativeInstrumentsOnCompanysFinancialPerformance</Role>
      <ShortName>Fair Value Measurements and Derivative Instruments - Effect of Derivative Instruments on Company's Financial Performance (Detail)</ShortName>
      <XmlFileName>R51.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>153 - Disclosure - Segment Reporting - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureSegmentReportingAdditionalInformation</Role>
      <ShortName>Segment Reporting - Additional Information (Detail)</ShortName>
      <XmlFileName>R52.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>154 - Disclosure - Segment Reporting - Segment Wide Reporting Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureSegmentReportingSegmentWideReportingInformation</Role>
      <ShortName>Segment Reporting - Segment Wide Reporting Information (Detail)</ShortName>
      <XmlFileName>R53.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>155 - Disclosure - Segment Reporting - Assets by Segment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureSegmentReportingAssetsBySegment</Role>
      <ShortName>Segment Reporting - Assets by Segment (Detail)</ShortName>
      <XmlFileName>R54.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>156 - Disclosure - Earnings Per Share - Reconciliation of Income from Operations Applicable to Common Shares and Computation of Diluted Weighted Average Shares Outstanding (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureEarningsPerShareReconciliationOfIncomeFromOperationsApplicableToCommonSharesAndComputationOfDilutedWeightedAverageSharesOutstanding</Role>
      <ShortName>Earnings Per Share - Reconciliation of Income from Operations Applicable to Common Shares and Computation of Diluted Weighted Average Shares Outstanding (Detail)</ShortName>
      <XmlFileName>R55.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>157 - Disclosure - Earnings Per Share - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureEarningsPerShareAdditionalInformation</Role>
      <ShortName>Earnings Per Share - Additional Information (Detail)</ShortName>
      <XmlFileName>R56.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>158 - Disclosure - Legal Proceedings and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.penx.com/taxonomy/role/DisclosureLegalProceedingsAndContingenciesAdditionalInformation</Role>
      <ShortName>Legal Proceedings and Contingencies - Additional Information (Detail)</ShortName>
      <XmlFileName>R57.xml</XmlFileName>
    </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 us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">'Monetary' elements on report '138 - Disclosure - Debt - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '139 - Disclosure - Income Taxes - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '153 - Disclosure - Segment Reporting - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '158 - Disclosure - Legal Proceedings and Contingencies - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 103 - Statement - Condensed Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Nov. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Aug. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 104 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 105 - Statement - Condensed Consolidated Statements of Operations</Log>
    <Log type="Info">Process Flow-Through: 106 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss)</Log>
    <Log type="Info">Process Flow-Through: 107 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 108 - Statement - Condensed Consolidated Statements of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>penx-20121130.xml</File>
    <File>penx-20121130.xsd</File>
    <File>penx-20121130_cal.xml</File>
    <File>penx-20121130_def.xml</File>
    <File>penx-20121130_lab.xml</File>
    <File>penx-20121130_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
