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Activity of Awarded Restricted Stock Units (Detail) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Restricted Stock Units (RSUs)    
Number of shares    
Balance at beginning of year (in shares) 500,850pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 [1]  
Granted (in shares) 191,483us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
Vested (in shares) (92,986)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
Forfeited (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
Balance at end of year (in shares) 599,347pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 [1]  
Weighted-Average Grant Date Fair Value    
Balance at beginning of year (in dollars per share) $ 4.42pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 [1]  
Granted (in dollars per share) $ 16.32us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
Vested (in dollars per share) $ 6.29us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
Forfeited (in dollars per share) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
Balance at end of year (in dollars per share) $ 7.93pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 [1]  
Performance Based Restricted Stock Units (PBRSUs)    
Number of shares    
Balance at beginning of year (in shares) 561,310pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Granted (in shares) 97,606us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Forfeited (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Balance at end of year (in shares) 658,916pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Weighted-Average Grant Date Fair Value    
Balance at beginning of year (in dollars per share) $ 16.07pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Granted (in dollars per share) $ 19.21us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Forfeited (in dollars per share) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Balance at end of year (in dollars per share) $ 16.29pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember		  
Retirement Eligible Employees, Equity Award | Restricted Stock Units (RSUs)    
Number of shares    
Balance at beginning of year (in shares)   346,777.000pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_VestingAxis
= pva_RetirementEligibleEmployeesEquityAwardMember
Balance at end of year (in shares) 346,777.000pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_VestingAxis
= pva_RetirementEligibleEmployeesEquityAwardMember		 346,777.000pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_VestingAxis
= pva_RetirementEligibleEmployeesEquityAwardMember
Minimum | Performance Based Restricted Stock Units (PBRSUs)    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage 0.00%pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesExpectedToVestPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		  
Maximum | Performance Based Restricted Stock Units (PBRSUs)    
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage 200.00%pva_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesExpectedToVestPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		  
[1] Excludes 346,777 units at the beginning of the year and 346,777 units at the end of year that have vested due to retirement eligibility, but have not yet been settled or converted to common shares.