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Note 8 - Fair Value Measurements (Details) - Fair Value, Assets Measured on Recurring Basis (Money Market Mutual Funds [Member], USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Note 8 - Fair Value Measurements (Details) - Fair Value, Assets Measured on Recurring Basis [Line Items]    
Money market mutual funds $ 26,358us-gaap_InvestmentsFairValueDisclosure $ 26,356us-gaap_InvestmentsFairValueDisclosure
Fair Value, Inputs, Level 1 [Member]
   
Note 8 - Fair Value Measurements (Details) - Fair Value, Assets Measured on Recurring Basis [Line Items]    
Money market mutual funds $ 26,358us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= pdfs_MoneyMarketMutualFundsMember
$ 26,356us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= pdfs_MoneyMarketMutualFundsMember