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Cover Page - shares
 9 Months Ended
Sep. 30, 2025
Oct. 29, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2025  
Document Transition Report false  
Entity File Number 001-02960  
Entity Registrant Name NPK International Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 72-1123385  
Entity Address, Address Line One 9320 Lakeside Boulevard,  
Entity Address, Address Line Two Suite 100  
Entity Address, City or Town The Woodlands,  
Entity Address, State or Province TX  
Entity Address, Postal Zip Code 77381  
City Area Code 281  
Local Phone Number 362-6800  
Title of 12(b) Security Common Stock, $0.01 par value  
Trading Symbol NPKI  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   84,494,699
Entity Central Index Key 0000071829  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q3  
Amendment Flag false