Annual report pursuant to Section 13 and 15(d)

Document And Entity Information

Document And Entity Information - USD ($)
12 Months Ended
Sep. 30, 2020
Nov. 06, 2020
Mar. 31, 2020
Document Information [Line Items]      
Entity Registrant Name Clearfield, Inc.    
Entity Central Index Key 0000796505    
Trading Symbol clfd    
Current Fiscal Year End Date --09-30    
Entity Filer Category Non-accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Emerging Growth Company false    
Entity Small Business true    
Entity Interactive Data Current Yes    
Entity Common Stock, Shares Outstanding (in shares)   13,649,962  
Entity Public Float     $ 130,912,520
Entity Shell Company false    
Document Type 10-K    
Document Period End Date Sep. 30, 2020    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Amendment Flag false    
Title of 12(b) Security Common Stock, $0.01 par value