v3.10.0.1
Document And Entity Information - shares
3 Months Ended
Nov. 30, 2018
Jan. 07, 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)   4,542,177
Document Type 10-Q  
Document Period End Date Nov. 30, 2018  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Amendment Flag false