DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	12 Months Ended
	Sep. 30, 2014 segment company	Sep. 30, 2013	Sep. 30, 2012
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Number of operating segments	3
Number of companies	2
Cash in non U.S. bank accounts	$ 34,500,000	$ 21,400,000
Debt instrument, interest rate, stated percentage		4.00%	4.00%
Fair value of insurance contracts	3,490,000
Trading securities		1,194,000
Contracts revenue	3,197,000
Contracts weighted average rate price (in Dollars per share)	$ 1.14
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax	(3,820,000)	20,113,000
Foreign currency transaction gain (loss), realized	141,000
Defined benefit plan, fair value of plan assets	154,966,000	153,731,000
Contract period	1 year
Income (loss) from operations	78,164,000	63,854,000	72,420,000
Provision for loss on contracts	3,100,000
Customer program reserves and cash discounts netted against accounts receivable	9,295,000	6,556,000
Costs in excess of billings, noncurrent	8,400,000	11,000,000
Unbilled contracts receivable	2,200,000	1,900,000
Depreciation, depletion and amortization, nonproduction	59,488,000	62,911,000	58,216,000
Accumulated capitalized interest costs	4,529,000	4,030,000	2,975,000
Original cost of fully depreciated property plant and equipment	253,272,000
Description of fair value calculation	Griffon used five year projections and a 3.0% terminal value to which discount rates between 9% and 10% were applied to calculate each unit’s fair value.
Fair value projections	5 years
Fair value terminal value	3.00%
Goodwill, impairment loss	0	0	0
Unrecognized tax benefits	7,906,000	10,520,000	11,876,000
Research and development arrangement, contract to perform for others, costs incurred, gross	23,400,000	22,400,000	23,600,000
Shipping, handling and transportation costs	42,400,000	39,600,000	40,200,000
Advertising revenue cost	24,000,000	23,000,000	22,000,000
Home & Building Products [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Income (loss) from operations	40,538,000	26,130,000	37,082,000
Number of components	2
Number of reporting units	1
Selling, general and administrative expenses [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Depreciation	10,815,000	12,733,000	13,136,000
U.S. Government [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Percentage of consolidated accounts receivable	16.00%
P & G [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Percentage of consolidated accounts receivable	7.00%
Home Depot [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Percentage of consolidated accounts receivable	9.00%
Contracts accounted for under percentage of completion [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Income (loss) from operations	(400,000)	3,400,000	9,200,000
Designated as hedging instrument [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Contracts revenue	4,975,000
Contracts weighted average rate price (in Dollars per share)	$ 1.14
Accumulated other comprehensive income (loss), foreign currency translation adjustment, before tax	386,000
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax	252,000
Gain (loss) on hedging activity		81,000
Level 1 [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Defined benefit plan, fair value of plan assets	78,229,000	81,552,000
Level 1 [Member] | Estimate of fair value measurement [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Available-for-sale securities	9,770,000
Level 1 [Member] | Portion at other than fair value measurement [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Available-for-sale securities	8,400,000
Level 2 [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Defined benefit plan, fair value of plan assets	76,737,000	72,179,000
Level 2 [Member] | Estimate of fair value measurement [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Trading securities	1,274,000
Level 2 [Member] | Portion at other than fair value measurement [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Trading securities	1,000,000
Senior notes [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Long-term debt, fair value	570,000,000
Convert. debt due 2017 [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Long-term debt, fair value	$ 110,188,000
Maximum [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Maturity period of highly liquid investments	3 months
Contracts expiration days	90 days
Fair value discount rates	10.00%
Finite-lived intangible asset, useful life		25 years
Maximum [Member] | Building and building improvements [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Property, plant and equipment, useful life	40 years
Maximum [Member] | Machinery and equipment [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Property, plant and equipment, useful life	15 years
Minimum [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Contracts expiration days	20 days
Fair value discount rates	9.00%
Finite-lived intangible asset, useful life		8 years
Minimum [Member] | Building and building improvements [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Property, plant and equipment, useful life	25 years
Minimum [Member] | Machinery and equipment [Member]
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) [Line Items]
Property, plant and equipment, useful life	2 years