DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Number of Operating Segments	3
Cash In Non U.S. Bank Accounts	$ 15,914	$ 39,738
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Fair Value Of Insurance Contracts	4,183
Trading Securities, Fair Value Disclosure	697
Contracts Revenue	1,500
Contracts Weighted Average Rate Price (in Dollars per share)	$ 0.966
Foreign Currency Transaction Gain (Loss), Realized	1
Defined Benefit Plan, Fair Value of Plan Assets	160,833	137,678
Accounts Receivable Percentage U.S. Government	18.00%
Accounts Receivable Percentage Home Depot And P&G	10.00%
Customer Program Reserves And Cash Discounts Netted Against Accounts Receivable	8,653	12,683
Depreciation, Depletion and Amortization, Nonproduction	58,216	52,844	38,456
Accumulated Capitalized Interest Costs	2,975	2,250	1,700
Original Cost Of Fully Depreciated Property Plant And Equipment	195,000
Description Of Fair Value Calculation	Griffon used five year projections and a 3.0% terminal value to which discount rates between 9.5% and 11.5% were applied to calculate each unit's fair value.
Unrecognized Tax Benefits	11,876	12,910	11,764
Research and Development Arrangement, Contract to Perform for Others, Costs Incurred, Gross	23,600	23,900	21,400
Shipping, Handling and Transportation Costs	40,200	41,600	32,100
Advertising Revenue Cost	22,000	23,000	14,700
General And Product Liability Claims Maximum Amount Of Per Occurrence	350
Workers Compensation And Automobile Liability Claims Maximum Amount Of Per Occurrence	250
Health Related Claims Amount Of Per Participant, Per Year	300
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	25 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	40 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	2 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	15 years
Minimum [Member]
Contracts Expiration Days	15 days
Maximum [Member]
Contracts Expiration Days	75 days
Senior Notes [Member]
Long-term Debt, Fair Value	580,250
Convertible Debt 2017 [Member]
Long-term Debt, Fair Value	102,000
Convertible Debt 2023 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Long-term Debt, Fair Value	$ 544