v3.19.1
Document And Entity Information - shares
6 Months Ended
Feb. 28, 2019
Apr. 08, 2019
Document Information [Line Items]    
Entity Registrant Name Northern Technologies International Corporation  
Entity Central Index Key 0000875582  
Trading Symbol ntic  
Current Fiscal Year End Date --08-31  
Entity Filer Category Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Emerging Growth Company false  
Entity Small Business true  
Entity Common Stock, Shares Outstanding (in shares)   4,537,408
Document Type 10-Q  
Document Period End Date Feb. 28, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Amendment Flag false