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Income Tax Disclosure (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Operating Loss Carryforwards [Line Items]        
Effective Income Tax Rate, Continuing Operations (50.00%)us-gaap_EffectiveIncomeTaxRateContinuingOperations (5.00%)us-gaap_EffectiveIncomeTaxRateContinuingOperations    
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate     38.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate  
Income Taxes Receivable $ 1,400,000us-gaap_IncomeTaxReceivable $ 600,000us-gaap_IncomeTaxReceivable    
Deferred Tax Assets, Tax Credit Carryforwards, Foreign 837,000us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsForeign 0us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsForeign    
Operating Loss Carryforwards 68,400,000us-gaap_OperatingLossCarryforwards      
R&E tax credit carryforward for future use 5,600,000pro_REtaxcreditcarryforwardforfutureuse      
Deferred Tax Assets, Operating Loss Carryforwards, Domestic 16,400,000us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic      
Unrealized excess tax benefit related to stock compensation 7,200,000pro_Unrealizedexcesstaxbenefitrelatedtostockcompensation      
Deferred tax asset, valuation allowance, domestic 16,200,000pro_Deferredtaxassetvaluationallowancedomestic      
Undistributed Earnings of Foreign Subsidiaries 300,000us-gaap_UndistributedEarningsOfForeignSubsidiaries      
Unrecognized Tax Benefits 395,000us-gaap_UnrecognizedTaxBenefits 349,000us-gaap_UnrecognizedTaxBenefits 349,000us-gaap_UnrecognizedTaxBenefits 349,000us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued 56,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued 3,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued 3,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued  
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit 0us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit      
Foreign tax paid 100,000pro_Foreigntaxpaid      
Cameleon Acquistion [Member]        
Operating Loss Carryforwards [Line Items]        
Operating Loss Carryforwards $ 33,800,000us-gaap_OperatingLossCarryforwards
/ us-gaap_BusinessAcquisitionAxis
= pro_CameleonAcquistionMember