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Business Acquisition (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended 0 Months Ended
Dec. 31, 2014
Sep. 28, 2014
Jun. 29, 2014
Mar. 30, 2014
Dec. 31, 2013
Sep. 29, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jan. 24, 2014
Business Acquisition [Line Items]                        
Net sales $ 142,034us-gaap_SalesRevenueNet $ 95,463us-gaap_SalesRevenueNet $ 88,312us-gaap_SalesRevenueNet $ 86,554us-gaap_SalesRevenueNet $ 134,990us-gaap_SalesRevenueNet $ 100,612us-gaap_SalesRevenueNet $ 101,396us-gaap_SalesRevenueNet $ 83,190us-gaap_SalesRevenueNet $ 412,363us-gaap_SalesRevenueNet $ 420,188us-gaap_SalesRevenueNet $ 472,490us-gaap_SalesRevenueNet  
Tech Ord [Member]                        
Business Acquisition [Line Items]                        
Business Combination, Consideration Transferred                       10,534us-gaap_BusinessCombinationConsiderationTransferred1
/ us-gaap_BusinessAcquisitionAxis
= npk_TechOrdMember
Cash Paid to Acquire Business     534us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_BusinessAcquisitionAxis
= npk_TechOrdMember
                10,000us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_BusinessAcquisitionAxis
= npk_TechOrdMember
Estimated Amount of Acquired Receivable Uncollectible                       20us-gaap_BusinessCombinationAcquiredReceivablesEstimatedUncollectible
/ us-gaap_BusinessAcquisitionAxis
= npk_TechOrdMember
Revenue of Acquiree Included in Conolidated Income Statement Since Acquisition Date                 13,732us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual
/ us-gaap_BusinessAcquisitionAxis
= npk_TechOrdMember
     
Earnings (Loss) of Acquiree Included in Conolidated Income Statement Since Acquisition Date                 $ 1,268us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual
/ us-gaap_BusinessAcquisitionAxis
= npk_TechOrdMember