Document And Entity Information (USD $)	12 Months Ended
	Sep. 30, 2011	Oct. 31, 2011	Mar. 31, 2011
Document and Entity Information [Abstract]
Entity Registrant Name	GRIFFON CORP
Document Type	10-K
Current Fiscal Year End Date	--09-30
Entity Common Stock, Shares Outstanding		61,497,463
Entity Public Float			$ 618,000,000
Amendment Flag	false
Entity Central Index Key	0000050725
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY