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Document And Entity Information
 3 Months Ended
Mar. 31, 2015
Document And Entity Information [Abstract]  
Document Type 10-Q
Amendment Flag false
Document Period End Date Mar. 31, 2015
Document Fiscal Year Focus 2015
Document Fiscal Period Focus Q1
Entity Registrant Name NEWMARKET CORP
Entity Central Index Key 0001282637
Current Fiscal Year End Date --12-31
Entity Filer Category Large Accelerated Filer
Entity Common Stock, Shares Outstanding 12,443,241dei_EntityCommonStockSharesOutstanding