NOTES PAYABLE, CAPITALIZED LEASES AND LONG-TERM DEBT (Detail) - Summary of Interest expense incurred (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010
Cash Interest	$ 45,984		$ 41,113		$ 7,263
Amortized Debt Discount	3,086		3,462		3,884
Amortized Deferred Cost & Other Fees	2,937		3,271		1,175
Total Interest Expense	52,007		47,846		12,322
Senior Notes [Member]
Effective Interest Rate	7.40%	[1]	7.40%	[1]		[1]
Cash Interest	39,188	[1]	21,118	[1]	0	[1]
Amortized Debt Discount	0	[1]	0	[1]	0	[1]
Amortized Deferred Cost & Other Fees	1,623	[1]	881	[1]	0	[1]
Total Interest Expense	40,811	[1]	21,999	[1]	0	[1]
Revolver Due 2016 [Member]
Effective Interest Rate		[1]		[1]		[1]
Cash Interest	881	[1]	0	[1]	0	[1]
Amortized Debt Discount	0	[1]	0	[1]	0	[1]
Amortized Deferred Cost & Other Fees	622	[1]	332	[1]	0	[1]
Total Interest Expense	1,503	[1]	332	[1]	0	[1]
Convertible Debt 2017 [Member]
Effective Interest Rate	9.20%	[2]	9.00%	[2]	9.10%	[2]
Cash Interest	4,000	[2]	3,944	[2]	3,240	[2]
Amortized Debt Discount	3,086	[2]	2,832	[2]	1,847	[2]
Amortized Deferred Cost & Other Fees	443	[2]	443	[2]	382	[2]
Total Interest Expense	7,529	[2]	7,219	[2]	5,469	[2]
Real Estate Mortgages Loan [Member]
Effective Interest Rate	4.00%	[3]	5.60%	[3]	6.40%	[3]
Cash Interest	575	[3]	761	[3]	487	[3]
Amortized Debt Discount	0	[3]	0	[3]	0	[3]
Amortized Deferred Cost & Other Fees	86	[3]	86	[3]	18	[3]
Total Interest Expense	661	[3]	847	[3]	505	[3]
Employee Stock Ownership Plan Loan [Member]
Effective Interest Rate	3.00%	[4]	2.70%	[4]	1.60%	[4]
Cash Interest	707	[4]	345	[4]	87	[4]
Amortized Debt Discount	0	[4]	0	[4]	0	[4]
Amortized Deferred Cost & Other Fees	6	[4]	67	[4]	0	[4]
Total Interest Expense	713	[4]	412	[4]	87	[4]
Capital Lease Obligations [Member]
Effective Interest Rate	5.30%	[5]	5.30%	[5]	5.20%	[5]
Cash Interest	551	[5]	602	[5]	634	[5]
Amortized Debt Discount	0	[5]	0	[5]	0	[5]
Amortized Deferred Cost & Other Fees	25	[5]	26	[5]	25	[5]
Total Interest Expense	576	[5]	628	[5]	659	[5]
Convertible Debt 2023 [Member]
Effective Interest Rate	4.00%	[6]	4.00%	[6]	9.40%	[6]
Cash Interest	21	[6]	20	[6]	2,021	[6]
Amortized Debt Discount	0	[6]	0	[6]	2,037	[6]
Amortized Deferred Cost & Other Fees	0	[6]	0	[6]	155	[6]
Total Interest Expense	21	[6]	20	[6]	4,213	[6]
Term Loan 2013 [Member]
Effective Interest Rate	5.00%	[7]		[7]		[7]
Cash Interest	831	[7]	338	[7]	0	[7]
Amortized Debt Discount	0	[7]	0	[7]	0	[7]
Amortized Deferred Cost & Other Fees	87	[7]	71	[7]	0	[7]
Total Interest Expense	918	[7]	409	[7]	0	[7]
Revolver Due 2012 [Member]
Effective Interest Rate		[7]		[7]		[7]
Cash Interest	102	[7]	90	[7]	0	[7]
Amortized Debt Discount	0	[7]	0	[7]	0	[7]
Amortized Deferred Cost & Other Fees	34	[7]	107	[7]	0	[7]
Total Interest Expense	136	[7]	197	[7]	0	[7]
Foreign Line of Credit [Member]
Effective Interest Rate	14.30%	[8]	3.00%	[8]		[8]
Cash Interest	228	[8]	91	[8]	0	[8]
Amortized Debt Discount	0	[8]	0	[8]	0	[8]
Amortized Deferred Cost & Other Fees	0	[8]	0	[8]	0	[8]
Total Interest Expense	228	[8]	91	[8]	0	[8]
Foreign Term Loan [Member]
Effective Interest Rate	10.50%	[8]		[8]		[8]
Cash Interest	238	[8]	0	[8]	0	[8]
Amortized Debt Discount	0	[8]	0	[8]	0	[8]
Amortized Deferred Cost & Other Fees	11	[8]	0	[8]	0	[8]
Total Interest Expense	249	[8]	0	[8]	0	[8]
Term Loan 2016 [Member]
Effective Interest Rate		[9]	9.50%	[9]	7.80%	[9]
Cash Interest	0	[9]	13,405	[9]	86	[9]
Amortized Debt Discount	0	[9]	572	[9]	0	[9]
Amortized Deferred Cost & Other Fees	0	[9]	838	[9]	0	[9]
Total Interest Expense	0	[9]	14,815	[9]	86	[9]
Asset Based Loan [Member]
Effective Interest Rate		[9]	6.20%	[9]	4.30%	[9]
Cash Interest	0	[9]	1,076	[9]	1,181	[9]
Amortized Debt Discount	0	[9]	58	[9]	0	[9]
Amortized Deferred Cost & Other Fees	0	[9]	341	[9]	404	[9]
Total Interest Expense	0	[9]	1,475	[9]	1,585	[9]
Revolver Due 2013 [Member]
Effective Interest Rate		[10]	1.20%	[10]	2.70%	[10]
Cash Interest	0	[10]	160	[10]	575	[10]
Amortized Debt Discount	0	[10]	0	[10]	0	[10]
Amortized Deferred Cost & Other Fees	0	[10]	79	[10]	191	[10]
Total Interest Expense	0	[10]	239	[10]	766	[10]
Other Long Term Debt [Member]
Cash Interest	557	[11]	104	[11]	39	[11]
Amortized Debt Discount	0	[11]	0	[11]	0	[11]
Amortized Deferred Cost & Other Fees	0	[11]	0	[11]	0	[11]
Total Interest Expense	557	[11]	104	[11]	39	[11]
Capitalized Interest [Member]
Cash Interest	(1,895)		(941)		(1,087)
Amortized Debt Discount	0		0		0
Amortized Deferred Cost & Other Fees	0		0		0
Total Interest Expense	$ (1,895)		$ (941)		$ (1,087)

[1] On March 17, 2011, in an unregistered offering through a private placement under Rule 144A, Griffon issued, at par, $550,000 of 7.125% Senior Notes due in 2018 ("Senior Notes"); interest is payable semi-annually. On August 9, 2011, Griffon exchanged all of the Senior Notes for substantially identical Senior Notes registered under the Securities Act of 1933 ("Senior Notes"), via an exchange offer.The Senior Notes can be redeemed prior to April 1, 2014 at a price of 100% of principal plus a make-whole premium and accrued interest; on or after April 1, 2014, the Senior Notes can be redeemed at a certain price (declining from 105.344% of principal on or after April 1, 2014 to 100% of principal on or after April 1, 2017), plus accrued interest. Proceeds from the Senior Notes were used to pay down the outstanding borrowings under a senior secured term loan facility and two senior secured revolving credit facilities of certain of the Company's subsidiaries. The Senior Notes are senior unsecured obligations of Griffon guaranteed by certain domestic subsidiaries, and are subject to certain covenants, limitations and restrictions.On March 18, 2011, Griffon entered into a five-year $200,000 Revolving Credit Facility ("Credit Agreement"), which includes a letter of credit sub-facility with a limit of $50,000, a multi-currency sub-facility of $50,000 and a swingline sub-facility with a limit of $30,000. Borrowings under the Credit Agreement may be repaid and re-borrowed at any time, subject to final maturity of the facility or the occurrence of a default or event of default under the Credit Agreement. Interest is payable on borrowings at either a LIBOR or base rate benchmark rate plus an applicable margin, which adjusts based on financial performance. The margins are 1.75% for base rate loans and 2.75% for LIBOR loans, in each case without a floor. The Credit Agreement has certain financial maintenance tests including a maximum total leverage ratio, a maximum senior secured leverage ratio and a minimum interest coverage ratio as well as customary affirmative and negative covenants and events of default. The Credit Agreement also includes certain restrictions, such as limitations on the incurrence of indebtedness and liens and the making of restricted payments and investments. Borrowings under the Credit Agreement are guaranteed by certain domestic subsidiaries and are secured, on a first priority basis, by substantially all assets of the Company and the guarantors.At September 30, 2012, there were $21,693 of standby letters of credit outstanding under the Credit Agreement; $178,307 was available for borrowing at that date.

[2] On December 21, 2009, Griffon issued $100,000 principal of 4% convertible subordinated notes due 2017 (the "2017 Notes"). The initial conversion rate of the 2017 Notes was 67.0799 shares of Griffon's common stock per $1,000 principal amount of notes, corresponding to an initial conversion price of $14.91 per share, a 23% conversion premium over the $12.12 closing price on December 15, 2009. When a cash dividend is declared that would result in an adjustment to the conversion ratio of less than 1%, any adjustment to the conversion ratio is deferred until the first to occur of (i) actual conversion, (ii) the 42nd trading day prior to maturity of the notes, and (iii) such time as the cumulative adjustment equals or exceeds 1%. As of September 30, 2012, based on aggregate dividends of $0.08 per share resulted in a cumulative change in the conversion rate of 0.86%. Griffon used 8.75% as the nonconvertible debt-borrowing rate to discount the 2017 Notes and will amortize the debt discount through January 2017. At issuance, the debt component of the 2017 Notes was $75,437 and debt discount was $24,563. At September 30, 2012 and September 30, 2011, the 2017 Notes had a capital in excess of par component, net of tax, of $15,720.

[3] On December 20, 2010, Griffon entered into two second lien real estate mortgages to secure new loans totaling $11,834. The loans mature in February 2016, are collateralized by the related properties and are guaranteed by Griffon. The loans bear interest at a rate of LIBOR plus 3% with the option to swap to a fixed rate. Griffon has other real estate mortgages, collateralized by real property, which bear interest at 6.3% and mature in 2016. On October 3, 2011, the mortgage at Russia, Ohio was paid in full, on maturity.

[4] Griffon's Employee Stock Ownership Plan ("ESOP") entered into a loan agreement in August 2010 to borrow $20,000 over a one-year period. The proceeds were used to purchase 1,874,737 shares of Griffon common stock in the open market for $19,973. The loan bears interest at a) LIBOR plus 2.5% or b) the lender's prime rate, at Griffon's option. In November 2011, Griffon exercised an option to convert the outstanding loan to a five-year term loan; principal is payable in quarterly installments of $250, beginning December 2011, with a balloon payment of $15,223 due at maturity (November 2016). The loan is secured by shares purchased with the proceeds of the loan, and repayment is guaranteed by Griffon. At September 30, 2012, $18,973 was outstanding.In addition, the ESOP has a loan agreement, guaranteed by Griffon, which requires quarterly principal payments of $156 and interest through the extended expiration date of December 2013 at which time the $3,125 balance of the loan, and any outstanding interest, will be payable. The primary purpose of this loan was to purchase 547,605 shares of Griffon's common stock in October 2008. The loan is secured by shares purchased with the proceeds of the loan, and repayment is guaranteed by Griffon. The loan bears interest at rates based upon the prime rate or LIBOR. At September 30, 2012, $3,750 was outstanding.

[5] In October 2006, CBP entered into a capital lease totaling $14,290 for real estate in Troy, Ohio. The lease matures in 2021, bears interest at a fixed rate of 5.1%, is secured by a mortgage on the real estate and is guaranteed by Griffon.

[6] At September 30, 2012 and September 30, 2011, Griffon had $532 of 4% convertible subordinated notes due 2023 (the "2023 Notes") outstanding. Holders of the 2023 Notes may require Griffon to repurchase all or a portion of their 2023 Notes on July 18, 2013 and 2018, if Griffon's common stock price is below the conversion price of the 2023 Notes, as well as upon a change in control. An adjustment to the conversion rate will be required as the result of payment of a cash dividend only if such adjustment would be greater than 1% (or at such time as the cumulative impact on the conversion rate reaches 1% in the aggregate). As of September 30, 2012, based on aggregate dividends of $0.08 per share resulted in a cumulative change in the conversion rate of 0.89%. At September 30, 2012 and September 30, 2011, the 2023 Notes had no capital in excess of par value component as substantially all of these notes were put to Griffon at par and settled in July 2010.

[7] In November 2010, Clopay Europe GMBH ("Clopay Europe") entered into a 10,000 revolving credit facility and a 20,000 term loan. The facility accrues interest at Euribor plus 2.1% per annum (2.3% at September 30, 2012), and the term loan accrues interest at Euribor plus 2.2% per annum (2.4% at September 30, 2012). The revolving facility matures in November 2012, but is renewable upon mutual agreement with the bank. Subsequent to September 30, 2012 the line was renewed for an additional year to November 2013. In July 2011, the full 20,000 was drawn on the Term Loan, with a portion of the proceeds used to repay borrowings under the revolving credit facility. The term loan is payable in ten equal quarterly installments which began in September 2011, with maturity in December 2013. Under the term loan, Clopay Europe is required to maintain a certain minimum equity to assets ratio and keep leverage below a certain level, defined as the ratio of total debt to EBITDA. At September 30, 2012, there were no borrowings on the revolving credit with 10,000 available for borrowing.

[8] In February 2012, Clopay do Brazil, a subsidiary of Plastics, borrowed $4,000 at a rate of 104.5% of Brazilian CDI (7.7% at September 30, 2012). The loan was used to refinance existing loans and is collateralized by accounts receivable and a 50% guaranty by Plastics and is to be repaid in four equal, semi-annual installments of principal plus accrued interest beginning in August 2012. Clopay do Brazil also maintains lines of credit of approximately $4,200. Interest on borrowings accrue at a rate of Brazilian CDI plus 6.0% or a fixed rate (13.8% or 10.2%, respectively, at September 30, 2012). At September 30, 2012 there was approximately $2,064 borrowed under the lines.

[9] In connection with the ATT acquisition, Clopay Ames True Temper Holding Corp. ("Clopay Ames"), a subsidiary of Griffon, entered into a $375,000 secured term Loan ("Term Loan") and a $125,000 asset based lending agreement ("ABL"). On November 30, 2010, Clopay Ames, as required under the Term Loan agreement, entered into an interest rate swap on a notional amount of $200,000 of the Term Loan. The agreement fixed the LIBOR component of the Term Loan interest rate at 2.085% for the notional amount of the swap. On March 17, 2011, the Term Loan and swap were terminated, and on March 18, 2011, the ABL was terminated, in connection with the issuance of the Senior Notes and Credit Agreement.

[10] In March 2008, Telephonics entered into a credit agreement with JPMorgan Chase Bank, N.A., as administrative agent, and the lenders party thereto, pursuant to which the lenders agreed to provide a five-year, revolving credit facility of $100,000 (the "TCA"). The TCA terminated in connection with the Credit Agreement.

[11] Includes capital leases.