| Cover Cover | Nov. 13, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 13, 2019 |
| Entity Registrant Name | GRIFFON CORPORATION |
| Entity Central Index Key | 0000050725 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-06620 |
| Entity Tax Identification Number | 11-1893410 |
| Entity Address, Address Line One | 712 Fifth Avenue, 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.25 par value |
| Trading Symbol | GFF |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
