LONG-TERM DEBT (Detail)	3 Months Ended		6 Months Ended		12 Months Ended		8 Months Ended	6 Months Ended		3 Months Ended				6 Months Ended				12 Months Ended				3 Months Ended					6 Months Ended				12 Months Ended				3 Months Ended				6 Months Ended				12 Months Ended			3 Months Ended				6 Months Ended				12 Months Ended			12 Months Ended		3 Months Ended					6 Months Ended								3 Months Ended							6 Months Ended														3 Months Ended				6 Months Ended	12 Months Ended
	Mar. 31, 2013 USD ($)	Dec. 31, 2011 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Sep. 30, 2011	Sep. 30, 2012 USD ($)	Aug. 31, 2010 Employee Stock Ownership Plan Loan [Member] USD ($)	Mar. 31, 2012 Brazilian CDI [Member] Foreign Term Loan [Member]	Sep. 30, 2011 Senior Notes [Member] USD ($)	Mar. 31, 2013 Real Estate Mortgages Loan [Member] USD ($)		Mar. 31, 2012 Real Estate Mortgages Loan [Member]		Mar. 31, 2013 Real Estate Mortgages Loan [Member] USD ($)		Mar. 31, 2012 Real Estate Mortgages Loan [Member]		Sep. 30, 2011 Real Estate Mortgages Loan [Member]	Sep. 30, 2012 Real Estate Mortgages Loan [Member] USD ($)		Mar. 31, 2012 Other Real Estate Mortgages Loan [Member]	Mar. 31, 2013 Employee Stock Ownership Plan Loan [Member] USD ($)		Dec. 31, 2012 Employee Stock Ownership Plan Loan [Member] USD ($)	Mar. 31, 2012 Employee Stock Ownership Plan Loan [Member]		Mar. 31, 2013 Employee Stock Ownership Plan Loan [Member] USD ($)		Mar. 31, 2012 Employee Stock Ownership Plan Loan [Member]		Sep. 30, 2011 Employee Stock Ownership Plan Loan [Member] USD ($)	Sep. 30, 2009 Employee Stock Ownership Plan Loan [Member]	Sep. 30, 2012 Employee Stock Ownership Plan Loan [Member] USD ($)		Mar. 31, 2013 Capital Lease Obligations [Member] USD ($)		Mar. 31, 2012 Capital Lease Obligations [Member]		Mar. 31, 2013 Capital Lease Obligations [Member] USD ($)		Mar. 31, 2012 Capital Lease Obligations [Member]		Sep. 30, 2007 Capital Lease Obligations [Member] USD ($)	Sep. 30, 2012 Capital Lease Obligations [Member] USD ($)		Mar. 31, 2013 Revolver Due 2013 [Member] USD ($)		Mar. 31, 2012 Revolver Due 2013 [Member]		Mar. 31, 2013 Revolver Due 2013 [Member] USD ($)		Mar. 31, 2012 Revolver Due 2013 [Member]		Sep. 30, 2011 Revolver Due 2013 [Member] EUR (€)	Sep. 30, 2012 Revolver Due 2013 [Member] USD ($)		Sep. 30, 2011 Term Loan [Member] EUR (€)	Mar. 31, 2013 Foreign Term Loan [Member] Brazilian CDI [Member]	Mar. 31, 2013 Foreign Term Loan [Member] USD ($)		Dec. 31, 2012 Foreign Term Loan [Member]	Mar. 31, 2012 Foreign Term Loan [Member]		Mar. 31, 2013 Foreign Term Loan [Member] USD ($)		Mar. 31, 2012 Foreign Term Loan [Member] USD ($)		Sep. 30, 2012 Foreign Term Loan [Member] USD ($)		Mar. 31, 2013 Foreign Line of Credit [Member] LIBOR Rate [Member]	Mar. 31, 2013 Foreign Line of Credit [Member] Bankers Acceptance Rate [Member]	Mar. 31, 2013 Foreign Line of Credit [Member] USD ($)		Mar. 31, 2013 Foreign Line of Credit [Member] CAD		Dec. 31, 2012 Foreign Line of Credit [Member] CAD	Mar. 31, 2012 Foreign Line of Credit [Member]		Mar. 31, 2013 Foreign Line of Credit [Member] USD ($)		Mar. 31, 2013 Foreign Line of Credit [Member] CAD		Mar. 31, 2012 Foreign Line of Credit [Member]		Sep. 30, 2012 Foreign Line of Credit [Member] USD ($)		Mar. 31, 2013 Convertible Debt 2023 [Member] USD ($)	Sep. 30, 2012 Convertible Debt 2023 [Member] USD ($)	Mar. 31, 2012 Convertible Debt 2023 [Member]	Mar. 31, 2013 Letter Of Credit Subfacility [Member] Revolver Due 2018 [Member] USD ($)	Mar. 28, 2013 Letter Of Credit Subfacility [Member] Revolver Due 2018 [Member] USD ($)	Mar. 28, 2013 Multicurrency Subfacility [Member] Revolver Due 2018 [Member] USD ($)	Mar. 28, 2013 Swingline Subfacility [Member] Revolver Due 2018 [Member] USD ($)	Mar. 28, 2013 Margin Rate [Member] Revolver Due 2018 [Member]	Mar. 28, 2013 LIBOR Rate [Member]	Mar. 31, 2013 Convertible Debt 2017 [Member] USD ($)	Mar. 31, 2013 Convertible Debt 2017 [Member] USD ($)	Sep. 30, 2012 Convertible Debt 2017 [Member] USD ($)	Sep. 30, 2010 Convertible Debt 2017 [Member]	Dec. 21, 2009 Convertible Debt 2017 [Member] USD ($)	Sep. 30, 2011 Employee Stock Ownership Plan Loan [Member] USD ($)	Aug. 31, 2010 Employee Stock Ownership Plan Loan [Member] USD ($)	Sep. 30, 2011 Revolver Due 2016 [Member] USD ($)	Mar. 31, 2013 Revolver Due 2018 [Member] USD ($)	Mar. 28, 2013 Revolver Due 2018 [Member] USD ($)
Debt Instrument, Face Amount						$ 11,834,000			$ 550,000,000																																																																																											$ 100,000,000		$ 20,000,000
Debt Instrument, Interest Rate, Stated Percentage									7.125%												6.30%																																																																				4.00%											4.00%
Debt Instrument Redemption Price Description					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.
Line of Credit Facility, Current Borrowing Capacity																																																																										15,000,000							15,000,000										60,000,000	50,000,000											200,000,000		225,000,000
Proceeds from Lines of Credit																																																																																													30,000,000
Line of Credit Facility, Interest Rate During Period																																																																																														1.25%	2.25%
Line of Credit Facility, Amount Outstanding																																																											4,186,000					4,186,000																										22,712,000
Line of Credit Facility, Remaining Borrowing Capacity																																																																																																								202,288,000
Debt Instrument, Convertible, Conversion Ratio																																																																																																67.8495
Debt Instrument, Convertible, Conversion Price (in Dollars per share)																																																																																																$ 14.74	$ 14.74
Debt Instrument, Convertible, Terms of Conversion Feature																																																																																																			1%
Last Conversion Price Adjustment (in Dollars per share)																																																																																																$ 0.025	$ 0.025
Potential Conversion Rate Adjustment																																																																																																0.22%	0.22%
Debt Instrument, Convertible, If-converted Value in Excess of Principal																																																																																																	15,720,000	15,720
Debt Instrument, Description of Variable Rate Basis																		The loans bear interest at a rate of LIBOR plus 3% with the option to swap to a fixed rate.													The loan bears interest at a) LIBOR plus 2.5% or b) the lender's prime rate, at Griffon's option.																							The facility accrues interest at EURIBOR plus 2.45% per annum and the term loan accrues interest at EURIBOR plus 2.20% per annum.
Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award (in Shares)							1,874,737
Stock Repurchased During Period, Value (in Dollars)	10,265	7,331,000					19,973,000
Debt Instrument, Periodic Payment, Principal																															250,000
Debt Instrument Balloon Payment																															15,223,000
Long-term Debt, Gross	713,257,000		713,257,000			716,217,000				13,652,000	[1]			13,652,000	[1]				14,063,000	[1]		21,911,000	[2]				21,911,000	[2]					22,723,000	[2]	9,995,000	[3]			9,995,000	[3]				10,455,000	[3]	0	[4]			0	[4]				0	[4]			1,732,000	[5]				1,732,000	[5]			2,693,000	[5]			4,186,000	[5]						4,186,000	[5]					2,064,000	[5]															18,473,000
Employee Stock Ownership Plan Debt Structure Required Quarterly Principal Payments																								156,000
Employee Stock Ownership Plan Debt Structure Balance Of Loan For Interest																								3,125,000
Stock Issued During Period, Shares, New Issues (in Shares)																																547,605
Employee Stock Ownership Plan (ESOP), Debt Structure, Employer Loan Guarantee																						3,438,000					3,438,000
Proceeds from Issuance of Long-term Debt			303,000	4,000,000																																							14,290,000																							4,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate																																											5.30%
Proceeds from Long-term Lines of Credit (in Euro)																																																						10,000,000			20,000,000																			15,000,000
Debt Instrument, Interest Rate During Period			6.00%					104.50%		5.40%	[1]	5.60%	[1]	5.40%	[1]	5.60%	[1]					2.90%	[2]		3.00%	[2]	2.90%	[2]	3.00%	[2]					5.20%	[3]	5.30%	[3]	5.30%	[3]	5.30%	[3]				0.50%	[4]		[4]	0.50%	[4]		[4]						9.80%	[5]		10.00%	[5]	10.20%	[5]	10.00%	[5]					12.30%	[5]	12.30%	[5]		9.10%	[5]	11.30%	[5]	11.30%	[5]	9.10%	[5]
Line of Credit Facility, Interest Rate Description																																																													7.0%															The facility accrues interest at LIBOR or the Bankers Acceptance Rate plus 1.3% per annum
Percentage Of Guaranty By Plastics																																																																		50.00%
Maintains Maximum Amount Of Line Of Credit																																																											4,400,000					4,400,000
Line of Credit Facility, Interest Rate at Period End																																																										13.00%												1.48%	1.49%
Proceeds from Long-term Lines of Credit (in Dollars)																																																						10,000,000			20,000,000																			15,000,000
Convertible Subordinated Debt																																																																																							$ 532,000	$ 532,000

[1] 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.

[2] 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 March 31, 2013, $18,473 was outstanding.In addition, the ESOP is party to a loan agreement 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. Griffon has the intent and ability to refinance the December 2013 balance, and has classified the balance in Long-Term Debt. 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 March 31, 2013, $3,438 was outstanding.

[3] 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 5.3%, is secured by a mortgage on the real estate and is guaranteed by Griffon.

[4] 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 2.45% per annum and the term loan accrues interest at EURIBOR plus 2.20% per annum. The revolving facility matures in November 2013, but is renewable upon mutual agreement with the bank. 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.

[5] In February 2012, Clopay do Brazil, a subsidiary of Plastics, borrowed $4,000 at a rate of 104.5% of Brazilian CDI (7.0% at March 31, 2013). The loan was used to refinance existing loans, 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 $4,400. Interest on borrowings accrue at a rate of Brazilian CDI plus 6.0% (13.0%, at March 31, 2013). At March 31, 2013 there was approximately $4,186 borrowed under the lines.In November 2012, Garant G.P. ("Garant") entered into a CAD $15,000 revolving credit facility. The facility accrues interest at LIBOR or the Bankers Acceptance Rate plus 1.3% per annum (1.48% and 1.49% as of March 31, 2013). The revolving facility matures in November 2015. Garant is required to maintain a certain minimum equity. At March 31, 2013, there were no borrowings under the revolving credit facility with CAD $15,000 available for borrowing