v3.19.2
Cover - shares
9 Months Ended
Jun. 30, 2019
Jul. 31, 2019
Cover page.    
Document Type 10-Q  
Amendment Flag false  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
Document Transition Report false  
Entity File Number 1-06620  
Entity Registrant Name GRIFFON CORPORATION  
Entity Central Index Key 0000050725  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 11-1893410  
Entity Address, Address Line One 712 Fifth Ave, 18th Floor  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10019  
City Area Code 212  
Local Phone Number 957-5000  
Title of 12(b) Security Common Stock, $0.25 par value  
Trading Symbol GFF  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   46,800,571