v3.26.1
Document and Entity Information
Aug. 13, 2026
Document And Entity Information [Line Items]  
Entity Registrant Name NEWMARKET CORP
Amendment Flag false
Entity Central Index Key 0001282637
Document Type 8-K
Document Period End Date Aug. 13, 2026
Entity File Number 1-32190
Entity Tax Identification Number 20-0812170
Entity Address, Address Line One 330 South Fourth Street
Entity Address, City or Town Richmond
Entity Address, State or Province VA
Entity Address, Postal Zip Code 23219
City Area Code (804)
Local Phone Number 788-5000
Written Communications false
Soliciting Material false
Pre Commencement Tender Offer false
Pre Commencement Issuer Tender Offer false
Security 12b Title Common Stock, without par value
Trading Symbol NEU
Security Exchange Name NYSE
Entity Emerging Growth Company false
VA  
Document And Entity Information [Line Items]  
Entity Incorporation State Country Code VA