Accounting Policies, by Policy (Policies)	12 Months Ended
Sep. 30, 2013
Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	Consolidation The consolidated financial statements include the accounts of Griffon and all subsidiaries. Intercompany accounts and transactions have been eliminated in consolidation.
Earnings Per Share, Policy [Policy Text Block]	Earnings (Loss) per share Due to rounding, the sum of earnings per share of Continuing operations and Discontinued operations may not equal earnings per share of Net income.
Discontinued Operations, Policy [Policy Text Block]	Discontinued operations – Installation Services In 2008, as a result of the downturn in the residential housing market, Griffon exited substantially all operating activities of its Installation Services segment which sold, installed and serviced garage doors and openers, fireplaces, floor coverings, cabinetry and a range of related building products, primarily for the new residential housing market. Operating results of substantially all of this segment have been reported as discontinued operations in the Consolidated Statements of Operations and Comprehensive Income (Loss) for all periods presented; the Installation Services segment is excluded from segment reporting. At September 30, 2013, Griffon’s assets and liabilities for discontinued operations primarily related to income taxes and product liability, warranty and environmental reserves.
Reclassifications and Adoption of New Accounting Guidance Policy [Text Block]	Reclassifications and adoption of new accounting guidance Certain amounts in prior years have been reclassified to conform to the current year presentation.
Use of Estimates, Policy [Policy Text Block]	Use of estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting periods. These estimates may be adjusted due to changes in economic, industry or customer financial conditions, as well as changes in technology or demand. Significant estimates include allowances for doubtful accounts receivable and returns, net realizable value of inventories, restructuring reserves, valuation of goodwill and intangible assets, percentage of completion method of accounting, pension assumptions, useful lives associated with depreciation and amortization of intangible and fixed assets, warranty reserves, sales incentive accruals, stock based compensation assumptions, income taxes and tax valuation reserves, environmental reserves, legal reserves, insurance reserves and the valuation of discontinued assets and liabilities, and the accompanying disclosures. These estimates are based on management’s best knowledge of current events and actions Griffon may undertake in the future. Actual results may ultimately differ from these estimates.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and equivalents Griffon considers all highly liquid investments purchased with an initial maturity of three months or less to be cash equivalents. Cash equivalents primarily consist of overnight commercial paper, highly-rated liquid money market funds backed by U.S. Treasury securities and U.S. Agency securities, as well as insured bank deposits. Griffon had cash in non-U.S. bank accounts of approximately $21,400 and $15,900 at September 30, 2013 and 2012, respectively. Substantially all U.S. cash and equivalents are covered by government insurance or backed by government securities. Griffon regularly evaluates the financial stability of all institutions and funds that hold its cash and equivalents.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Fair value of financial instruments The carrying values of cash and equivalents, accounts receivable, accounts and notes payable and revolving credit debt approximate fair value due to either the short-term nature of such instruments or the fact that the interest rate of the revolving credit debt is based upon current market rates. The fair values of Griffon’s 2018 senior notes and 2017 4% convertible notes approximated $583,000 and $112,600, respectively, on September 30, 2013. Fair values were based upon quoted market prices (level 1 inputs). Insurance contracts with a value of $3,789 and $4,183 and trading securities with a value of $1,194 and $697 at September 30, 2013 and 2012, respectively, are measured and recorded at fair value based upon quoted prices in active markets for identical assets (level 2 inputs) and are included in Other current assets on the consolidated balance sheet. Items Measured at Fair Value on a Recurring Basis In the normal course of business, Griffon’s operations are exposed to the effect of changes in foreign currency exchange rates. In order to manage these risks, Griffon may enter into various derivative contracts such as foreign currency exchange contracts, including forwards and options. During 2013, Griffon entered into several such contracts in order to lock into a foreign currency rate for planned settlements of inter-company liabilities payable in USD. At inception, these hedges were all deemed effective as cash flow hedges with gains and losses related to changes in fair value deferred and recorded in Other comprehensive income (loss) and Prepaid and other current assets until settlement. Upon settlement, gains and losses were recognized in the Consolidated Statements of Operations and Comprehensive Income (Loss) as Other income. A gain of $81 was recorded in Other Income in 2013 for the settled contacts and there were 0 unsettled contracts that qualify for hedge accounting as of September 30, 2013. At September 30, 2013, Griffon had $750 of Australian dollar contracts at a weighted average rate of $1.07. The contracts, which protect Australia operations from currency fluctuations for U.S. dollar based purchases, do not qualify for hedge accounting and a fair value loss of $46 was recorded in Accrued liabilities and to Other income, net for the outstanding contracts, based on similar contract values (level 2 inputs), for the year ended September 30, 2013, respectively. All contracts expire in 15 to 90 days. Pension plan assets with a fair value of $153,731 at September 30, 2013, are measured and recorded at fair value based upon quoted prices in active markets for identical assets (level 1 inputs), quoted market prices for similar assets (level 2 inputs) and derived from audited financial statements (level 3 inputs).
Foreign Currency Transactions and Translations Policy [Policy Text Block]	Non-U.S. currency translation Assets and liabilities of non-U.S. subsidiaries, where the functional currency is not the U.S. dollar, have been translated at year-end exchange rates and profit and loss accounts have been translated using weighted average exchange rates. Adjustments resulting from currency translation have been recorded in the equity section of the balance sheet in Accumulated other comprehensive loss as cumulative translation adjustments. Cumulative translation adjustments were $20,113 and $23,202 at September 30, 2013 and 2012, respectively. Assets and liabilities of an entity that are denominated in currencies other than that entity’s functional currency are remeasured into the functional currency using period end exchange rates, or historical rates where applicable to certain balances. Gains and losses arising on remeasurements are recorded within the Consolidated Statement of Operations and Comprehensive Income (Loss) as a component of Other income (expense).
Revenue Recognition, Policy [Policy Text Block]	Revenue recognition Revenue is recognized when the following circumstances are satisfied: a) persuasive evidence of an arrangement exists, b) delivery has occurred, title has transferred or services are rendered, c) price is fixed and determinable and d) collectability is reasonably assured.Goods are sold on terms which transfer title and risk of loss at a specified location. Revenue recognition from product sales occurs when all factors are met, including transfer of title and risk of loss, which occurs either upon shipment or upon receipt by customers at the location specified in the terms of sale. Other than standard product warranty provisions, sales arrangements provide for no other significant post-shipment obligations. From time to time and for certain customers, rebates and other sales incentives, promotional allowances or discounts are offered, typically related to customer purchase volumes, all of which are fixed or determinable and are classified as a reduction of revenue and recorded at the time of sale. Griffon provides for sales returns allowances based upon historical returns experience. Telephonics earns a substantial portion of its revenue as either a prime or subcontractor from contract awards with the U.S. Government, as well as non-U.S. governments and other commercial customers. These formal contracts are typically long-term in nature, usually greater than one year. Revenue and profits from these long-term fixed price contracts are recognized under the percentage-of-completion method of accounting. Revenue and profits on fixed-price contracts that contain engineering as well as production requirements are recorded based on the ratio of total actual incurred costs to date to the total estimated costs for each contract (cost-to-cost method). Using the cost-to-cost method, revenue is recorded at amounts equal to the ratio of actual cumulative costs incurred divided by total estimated costs at completion, multiplied by the total estimated contract revenue, less the cumulative revenue recognized in prior periods. The profit recorded on a contract using this method is equal to the current estimated total profit margin multiplied by the cumulative revenue recognized, less the amount of cumulative profit previously recorded for the contract in prior periods. As this method relies on the substantial use of estimates, these projections may be revised throughout the life of a contract. Components of this formula and ratio that may be estimated include gross profit margin and total costs at completion. The cost performance and estimates to complete on long-term contracts are reviewed, at a minimum, on a quarterly basis, as well as when information becomes available that would necessitate a review of the current estimate. Adjustments to estimates for a contract’s estimated costs at completion and estimated profit or loss often are required as experience is gained, and as more information is obtained, even though the scope of work required under the contract may or may not change, or if contract modifications occur. The impact of such adjustments or changes to estimates is made on a cumulative basis in the period when such information has become known. Gross profit is affected by a variety of factors, including the mix of products, systems and services, production efficiencies, price competition and general economic conditions. Revenue and profits on cost-reimbursable type contracts are recognized as allowable costs, and are incurred on the contract at an amount equal to the allowable costs plus the estimated profit on those costs. The estimated profit on a cost-reimbursable contract may be fixed or variable based on the contractual fee arrangement. Incentive and award fees on these contracts are recorded as revenue when the criteria under which they are earned are reasonably assured of being met and can be estimated. For contracts whose anticipated total costs exceed the total expected revenue, an estimated loss is recognized in the period when identifiable. A provision for the entire amount of the estimated loss is recorded on a cumulative basis. Amounts representing contract change orders or claims are included in revenue only when they can be reliably estimated and their realization is probable, and are determined on a percentage-of-completion basis measured by the cost-to-cost method. From time to time, Telephonics may combine contracts if they are negotiated together, have specific requirements to combine, or are otherwise closely related. Contracts are segmented based on customer requirements.
Accounts Receivable Allowance for Doubtful Accounts and Concentrations of Credit Risk [Policy Text Block]	Accounts receivable, allowance for doubtful accounts and concentrations of credit risk Accounts receivable is composed principally of trade accounts receivable that arise primarily from the sale of goods or services on account and is stated at historical cost. A substantial portion of Griffon’s trade receivables are from customers of HBP, of which the largest customer is Home Depot, whose financial condition is dependent on the construction and related retail sectors of the economy. In addition, a significant portion of Griffon’s trade receivables are from one Plastics customer, P&G, whose financial condition is dependent on the consumer products and related sectors of the economy. As a percentage of consolidated accounts receivable, U.S. Government related programs were 19%, P&G was 12% and Home Depot was 10%. Griffon performs continuing evaluations of the financial condition of its customers, and although Griffon generally does not require collateral, letters of credit may be required from customers in certain circumstances. Trade receivables are recorded at the stated amount, less allowance for doubtful accounts and, when appropriate, for customer program reserves and cash discounts. The allowance represents estimated uncollectible receivables associated with potential customer defaults on contractual obligations (usually due to customers’ potential insolvency). The allowance for doubtful accounts includes amounts for certain customers where a risk of default has been specifically identified, as well as an amount for customer defaults based on a formula when it is determined the risk of some default is probable and estimable, but cannot yet be associated with specific customers. The provision related to the allowance for doubtful accounts is recorded in SG&A expenses. The Company writes-off accounts receivable when they are deemed to be uncollectible. Customer program reserves and cash discounts are netted against accounts receivable when it is customer practice to reduce invoices for these amounts. The amount netted against accounts receivable in 2013 and 2012 was $6,556 and $8,653, respectively.
Contract Costs and Recognized Income Not Yet Billed [Policy Text Block]	Contract costs and recognized income not yet billed Contract costs and recognized income not yet billed consists of amounts accounted for under the percentage of completion method of accounting, recoverable costs and accrued profit that cannot yet be invoiced under the terms of certain long-term contracts. Amounts will be invoiced when applicable contract terms, such as the achievement of specified milestones or product delivery, are met.
Inventory, Policy [Policy Text Block]	Inventories Inventories, stated at the lower of cost (first-in, first-out or average) or market, include material, labor and manufacturing overhead costs. Griffon’s businesses typically do not require inventory that is susceptible to becoming obsolete or dated. In general, Telephonics sells products in connection with programs authorized and approved under contracts awarded by the U.S. Government or agencies thereof and in accordance with customer specifications. Plastics primarily produces fabricated materials used by customers in the production of their products and these materials are produced against orders from those customers. HBP produces doors and non-powered lawn and garden tools in response to orders from customers of retailers and dealers or based on expected orders, as applicable.
Property, Plant and Equipment, Policy [Policy Text Block]	Property, plant and equipment Property, plant and equipment includes the historical cost of land, buildings, equipment and significant improvements to existing plant and equipment. Expenditures for maintenance, repairs and minor renewals are expensed as incurred. When property or equipment is sold or otherwise disposed of, the related cost and accumulated depreciation is removed from the respective accounts and the gain or loss is recognized. Depreciation expense, which includes amortization of assets under capital leases, was $62,911, $58,216 and $52,844 for the years ended September 30, 2013, 2012 and 2011, respectively, and was calculated on a straight-line basis over the estimated useful lives of the assets. Estimated useful lives for property, plant and equipment are as follows: buildings and building improvements, 25 to 40 years; machinery and equipment, 2 to 15 years and leasehold improvements, over the term of the lease or life of the improvement, whichever is shorter. Capitalized interest costs included in Property, plant and equipment were $4,030, $2,975 and $2,250 for the years ended September 30, 2013, 2012 and 2011, respectively. The original cost of fully-depreciated property, plant and equipment remaining in use at September 30, 2013 was approximately $216,000.
Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived, Policy [Policy Text Block]	Goodwill and indefinite-lived intangibles Goodwill is the excess of the acquisition cost of a business over the fair value of the identifiable net assets acquired. Goodwill is not amortized, but is subject to an annual impairment test unless during an interim period, impairment indicators, such as a significant change in the business climate, exist. Griffon performed its annual impairment testing of goodwill as of September 30, 2013. The performance of the test involves a two-step process. The first step involves comparing the fair value of Griffon’s reporting units with the reporting unit’s carrying amount, including goodwill. Griffon generally determines the fair value of its reporting units using the income approach methodology of valuation that includes the present value of expected future cash flows. This method uses market assumptions specific to Griffon’s reporting units. If the carrying amount of a reporting unit exceeds the reporting unit’s fair value, Griffon performs the second step of the goodwill impairment test to determine the amount of impairment loss. The second step compares the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill. Griffon defines its reporting units as its three segments. Griffon used five year projections and a 3.0% terminal value to which discount rates between 9% and 11.25% were applied to calculate each unit’s fair value. To substantiate fair values derived from the income approach methodology of valuation, the implied fair value was reconciled to Griffon’s market capitalization, the results of which supported the implied fair values. Any changes in key assumptions or management judgment with respect to a reporting unit or its prospects, which may result from a decline in Griffon’s stock price, a change in market conditions, market trends, interest rates or other factors outside Griffon’s control, or significant underperformance relative to historical or project future operating results, could result in a significantly different estimate of the fair value of the reporting units, which could result in a future impairment charge. Based upon the results of the annual impairment review, it was determined that the fair value of each reporting unit substantially exceeded the carrying value of the assets, as performed under step one, and no impairment existed. Similar to goodwill, Griffon tests indefinite-lived intangible assets at least annually and when indicators of impairment exist. Griffon uses a discounted cash flow method to calculate and compare the fair value of the intangible to its book value. This method uses market assumptions specific to Griffon’s reporting units, which are reasonable and supportable. If the fair value is less than the book value of the indefinite-lived intangibles, an impairment charge would be recognized. There was 0 impairment related to any goodwill or indefinite-lived intangible assets in 2013, 2012 or 2011.
Definite Lived Long Lived Assets [Policy Text Block]	Definite-lived long-lived assets Amortizable intangible assets are carried at cost less accumulated amortization. For financial reporting purposes, definite-lived intangible assets are amortized on a straight-line basis over their useful lives, generally eight to twenty-five years. Long-lived assets and certain identifiable intangible assets to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. There were no indicators of impairment during the three years ending September 30, 2013
Income Tax, Policy [Policy Text Block]	Income taxes Income taxes are accounted for under the liability method. Deferred taxes reflect the tax consequences on future years of differences between the tax basis of assets and liabilities and their financial reporting amounts. The carrying value of Griffon’s deferred tax assets is dependent upon Griffon’s ability to generate sufficient future taxable income in certain tax jurisdictions. Should Griffon determine that it is more likely than not that some portion of the deferred tax assets will not be realized, a valuation allowance against the deferred tax assets would be established in the period such determination was made. Griffon provides for uncertain tax positions and any related interest and penalties based upon Management’s assessment of whether a tax benefit is more likely than not of being sustained upon examination by tax authorities. At September 30, 2013 Griffon believes that it has appropriately accounted for all unrecognized tax benefits. As of September 30, 2013, 2012 and 2011, Griffon has recorded unrecognized tax benefits in the amount of $10,520, $11,876 and $12,910, respectively. Accrued interest and penalties related to income tax matters are recorded in the provision for income taxes.
Research Development Costs Shipping and Handling Costs and Advertising Costs [Policy Text Block]	Research and development costs, shipping and handling costs and advertising costs Research and development costs not recoverable under contractual arrangements are charged to SG&A expense as incurred and amounted to $22,400, $23,600 and $23,900 in 2013, 2012 and 2011, respectively. Selling, general and administrative (“SG&A”) expenses include shipping and handling costs of $39,600 in 2013, $40,200 in 2012 and $41,600 in 2011 and advertising costs, which are expensed as incurred, of $23,000 in 2013, $22,000 in 2012 and $23,000 in 2011.
Risk Retention and Insurance [Policy Text Block]	Risk, retention and insurance Griffon’s property and casualty insurance programs contain various deductibles that, based on Griffon’s experience, are reasonable and customary for a company of its size and risk profile. Griffon generally maintains deductibles for claims and liabilities related primarily to workers’ compensation, general, product and automobile liability as well as property damage and business interruption losses resulting from certain events. Griffon does not consider any of the deductibles to represent a material risk to Griffon. Griffon accrues for claim exposures that are probable of occurrence and can be reasonably estimated. Insurance is maintained to transfer risk beyond the level of self-retention and provides protection on both an individual claim and annual aggregate basis. In the U.S., Griffon currently self-assumes its general and product liability claims up to $350 per occurrence and its workers’ compensation and automobile liability claims up to $250 per occurrence. Third-party insurance provides primary level coverage in excess of these deductible amounts up to certain specified limits. In addition, Griffon has excess liability insurance from third-party insurers on both an aggregate and an individual occurrence basis substantially in excess of the limits of the primary coverage. Griffon has local insurance coverage in Germany, Canada, Brazil, Australia, Turkey, China, Sweden, and Mexico. Griffon has worldwide excess coverage above these local programs. Griffon Corporation and its U.S. subsidiaries also self insures health related claims to a maximum of $300 per participant, per year.
Pension and Other Postretirement Plans, Policy [Policy Text Block]	Pension benefits Griffon sponsors defined and supplemental benefit pension plans for certain active and retired employees. Annual amounts relating to these plans are recorded based on actuarial projections, which include various actuarial assumptions, including discount rates, assumed rates of return, compensation increases and turnover rates. The actuarial assumptions used to determine pension liabilities and assets, as well as pension expense, are reviewed on an annual basis when modifications to assumptions are made based on current economic conditions and trends. The expected return on plan assets is determined based on the nature of the plans’ investments and expectations for long-term rates of return. The discount rate used to measure obligations is based on a corporate bond spot-rate yield curve that matches projected future benefit payments with the appropriate spot rate applicable to the timing of the projected future benefit payments. The assumptions utilized in recording Griffon’s obligations under the defined benefit pension plans are believed to be reasonable based on experience and advice from independent actuaries; however, differences in actual experience or changes in the assumptions may materially affect Griffon’s financial position or results of operations. The U.S. components of the defined benefit plans, which excludes the supplemental and post retirement healthcare and insurance benefit plans, are frozen and have ceased accruing benefits.
Newly Issued But Not Yet Effective Accounting Pronouncements [Policy Text Block]	*Newly issued but not yet effective accounting pronouncements* In February 2013, the FASB issued new accounting guidance requiring enhanced disclosures for items reclassified out of accumulated other comprehensive income. The guidance does not amend any existing requirements for reporting net income or other comprehensive income in the financial statements. This guidance is effective prospectively for annual reporting periods beginning after December 15, 2012, with early adoption permitted. As this new guidance is related to presentation only, the implementation of this guidance in the first quarter of fiscal year 2014 will not have a material effect on the Company’s financial condition or results of operations. In July 2013, the FASB issued new accounting guidance requiring an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss or tax credit carryforward, except for instances when the carryforward is not available to settle any additional income taxes and an entity does not intend to use the deferred tax benefit for these purposes. In these circumstances, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. This guidance is effective for the Company beginning in 2015 and is not expected to have a material impact on the Company’s financial condition or results of operations.
New Accounting Pronouncements, Policy [Policy Text Block]	*Recently issued effective accounting pronouncements* In June 2011, the FASB issued new accounting guidance requiring the presentation of comprehensive income, the components of net income, and the components of other comprehensive income either in a single continuous statement of comprehensive income, or in two separate but consecutive statements. The new accounting rules eliminate the option to present components of other comprehensive income as part of the statement of changes in shareholders’ equity. The new accounting rules were effective for the Company beginning in 2013 and did not have a material effect on the Company’s financial condition or results of operations and the Company presented comparable financial results. In September 2011, the FASB issued new accounting guidance that allows an entity to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative impairment testing of goodwill and indefinite life intangibles. This guidance is effective for the Company beginning in 2013 and did not have an impact on the Company’s financial condition or results of operations. The Company has implemented all new accounting pronouncements that are in effect and that may impact its financial statements and does not believe that there are any other new accounting pronouncements that have been issued that might have a material impact on its financial position or results of operations.

Accounting Policies, by Policy (Policies)

12 Months Ended

Sep. 30, 2013

Consolidation, Policy [Policy Text Block]

Consolidation

The consolidated financial statements include the accounts of Griffon and all subsidiaries. Intercompany accounts and transactions have been eliminated in consolidation.

Earnings Per Share, Policy [Policy Text Block]

Earnings (Loss) per share

Due to rounding, the sum of earnings per share of Continuing operations and Discontinued operations may not equal earnings per share of Net income.

Discontinued Operations, Policy [Policy Text Block]

Discontinued operations – Installation Services

In 2008, as a result of the downturn in the residential housing market, Griffon exited substantially all operating activities of its Installation Services segment which sold, installed and serviced garage doors and openers, fireplaces, floor coverings, cabinetry and a range of related building products, primarily for the new residential housing market. Operating results of substantially all of this segment have been reported as discontinued operations in the Consolidated Statements of Operations and Comprehensive Income (Loss) for all periods presented; the Installation Services segment is excluded from segment reporting.

At September 30, 2013, Griffon’s assets and liabilities for discontinued operations primarily related to income taxes and product liability, warranty and environmental reserves.

Reclassifications and Adoption of New Accounting Guidance Policy [Text Block]

Reclassifications and adoption of new accounting guidance

Certain amounts in prior years have been reclassified to conform to the current year presentation.

Use of Estimates, Policy [Policy Text Block]

Use of estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting periods. These estimates may be adjusted due to changes in economic, industry or customer financial conditions, as well as changes in technology or demand. Significant estimates include allowances for doubtful accounts receivable and returns, net realizable value of inventories, restructuring reserves, valuation of goodwill and intangible assets, percentage of completion method of accounting, pension assumptions, useful lives associated with depreciation and amortization of intangible and fixed assets, warranty reserves, sales incentive accruals, stock based compensation assumptions, income taxes and tax valuation reserves, environmental reserves, legal reserves, insurance reserves and the valuation of discontinued assets and liabilities, and the accompanying disclosures. These estimates are based on management’s best knowledge of current events and actions Griffon may undertake in the future. Actual results may ultimately differ from these estimates.

Cash and Cash Equivalents, Policy [Policy Text Block]

Cash and equivalents

Griffon considers all highly liquid investments purchased with an initial maturity of three months or less to be cash equivalents. Cash equivalents primarily consist of overnight commercial paper, highly-rated liquid money market funds backed by U.S. Treasury securities and U.S. Agency securities, as well as insured bank deposits. Griffon had cash in non-U.S. bank accounts of approximately $21,400 and $15,900 at September 30, 2013 and 2012, respectively. Substantially all U.S. cash and equivalents are covered by government insurance or backed by government securities. Griffon regularly evaluates the financial stability of all institutions and funds that hold its cash and equivalents.

Fair Value of Financial Instruments, Policy [Policy Text Block]

Fair value of financial instruments

The carrying values of cash and equivalents, accounts receivable, accounts and notes payable and revolving credit debt approximate fair value due to either the short-term nature of such instruments or the fact that the interest rate of the revolving credit debt is based upon current market rates.

The fair values of Griffon’s 2018 senior notes and 2017 4% convertible notes approximated $583,000 and $112,600, respectively, on September 30, 2013. Fair values were based upon quoted market prices (level 1 inputs).

Insurance contracts with a value of $3,789 and $4,183 and trading securities with a value of $1,194 and $697 at September 30, 2013 and 2012, respectively, are measured and recorded at fair value based upon quoted prices in active markets for identical assets (level 2 inputs) and are included in Other current assets on the consolidated balance sheet.

Items Measured at Fair Value on a Recurring Basis

In the normal course of business, Griffon’s operations are exposed to the effect of changes in foreign currency exchange rates. In order to manage these risks, Griffon may enter into various derivative contracts such as foreign currency exchange contracts, including forwards and options. During 2013, Griffon entered into several such contracts in order to lock into a foreign currency rate for planned settlements of inter-company liabilities payable in USD. At inception, these hedges were all deemed effective as cash flow hedges with gains and losses related to changes in fair value deferred and recorded in Other comprehensive income (loss) and Prepaid and other current assets until settlement. Upon settlement, gains and losses were recognized in the Consolidated Statements of Operations and Comprehensive Income (Loss) as Other income. A gain of $81 was recorded in Other Income in 2013 for the settled contacts and there were 0 unsettled contracts that qualify for hedge accounting as of September 30, 2013.

At September 30, 2013, Griffon had $750 of Australian dollar contracts at a weighted average rate of $1.07. The contracts, which protect Australia operations from currency fluctuations for U.S. dollar based purchases, do not qualify for hedge accounting and a fair value loss of $46 was recorded in Accrued liabilities and to Other income, net for the outstanding contracts, based on similar contract values (level 2 inputs), for the year ended September 30, 2013, respectively. All contracts expire in 15 to 90 days.

Pension plan assets with a fair value of $153,731 at September 30, 2013, are measured and recorded at fair value based upon quoted prices in active markets for identical assets (level 1 inputs), quoted market prices for similar assets (level 2 inputs) and derived from audited financial statements (level 3 inputs).

Foreign Currency Transactions and Translations Policy [Policy Text Block]

Non-U.S. currency translation

Assets and liabilities of non-U.S. subsidiaries, where the functional currency is not the U.S. dollar, have been translated at year-end exchange rates and profit and loss accounts have been translated using weighted average exchange rates. Adjustments resulting from currency translation have been recorded in the equity section of the balance sheet in Accumulated other comprehensive loss as cumulative translation adjustments. Cumulative translation adjustments were $20,113 and $23,202 at September 30, 2013 and 2012, respectively. Assets and liabilities of an entity that are denominated in currencies other than that entity’s functional currency are remeasured into the functional currency using period end exchange rates, or historical rates where applicable to certain balances. Gains and losses arising on remeasurements are recorded within the Consolidated Statement of Operations and Comprehensive Income (Loss) as a component of Other income (expense).

Revenue Recognition, Policy [Policy Text Block]

Revenue recognition

Revenue is recognized when the following circumstances are satisfied: a) persuasive evidence of an arrangement exists, b) delivery has occurred, title has transferred or services are rendered, c) price is fixed and determinable and d) collectability is reasonably assured.Goods are sold on terms which transfer title and risk of loss at a specified location. Revenue recognition from product sales occurs when all factors are met, including transfer of title and risk of loss, which occurs either upon shipment or upon receipt by customers at the location specified in the terms of sale. Other than standard product warranty provisions, sales arrangements provide for no other significant post-shipment obligations. From time to time and for certain customers, rebates and other sales incentives, promotional allowances or discounts are offered, typically related to customer purchase volumes, all of which are fixed or determinable and are classified as a reduction of revenue and recorded at the time of sale. Griffon provides for sales returns allowances based upon historical returns experience.

Telephonics earns a substantial portion of its revenue as either a prime or subcontractor from contract awards with the U.S. Government, as well as non-U.S. governments and other commercial customers. These formal contracts are typically long-term in nature, usually greater than one year. Revenue and profits from these long-term fixed price contracts are recognized under the percentage-of-completion method of accounting. Revenue and profits on fixed-price contracts that contain engineering as well as production requirements are recorded based on the ratio of total actual incurred costs to date to the total estimated costs for each contract (cost-to-cost method). Using the cost-to-cost method, revenue is recorded at amounts equal to the ratio of actual cumulative costs incurred divided by total estimated costs at completion, multiplied by the total estimated contract revenue, less the cumulative revenue recognized in prior periods. The profit recorded on a contract using this method is equal to the current estimated total profit margin multiplied by the cumulative revenue recognized, less the amount of cumulative profit previously recorded for the contract in prior periods. As this method relies on the substantial use of estimates, these projections may be revised throughout the life of a contract. Components of this formula and ratio that may be estimated include gross profit margin and total costs at completion. The cost performance and estimates to complete on long-term contracts are reviewed, at a minimum, on a quarterly basis, as well as when information becomes available that would necessitate a review of the current estimate. Adjustments to estimates for a contract’s estimated costs at completion and estimated profit or loss often are required as experience is gained, and as more information is obtained, even though the scope of work required under the contract may or may not change, or if contract modifications occur. The impact of such adjustments or changes to estimates is made on a cumulative basis in the period when such information has become known. Gross profit is affected by a variety of factors, including the mix of products, systems and services, production efficiencies, price competition and general economic conditions.

Revenue and profits on cost-reimbursable type contracts are recognized as allowable costs, and are incurred on the contract at an amount equal to the allowable costs plus the estimated profit on those costs. The estimated profit on a cost-reimbursable contract may be fixed or variable based on the contractual fee arrangement. Incentive and award fees on these contracts are recorded as revenue when the criteria under which they are earned are reasonably assured of being met and can be estimated.

For contracts whose anticipated total costs exceed the total expected revenue, an estimated loss is recognized in the period when identifiable. A provision for the entire amount of the estimated loss is recorded on a cumulative basis.

Amounts representing contract change orders or claims are included in revenue only when they can be reliably estimated and their realization is probable, and are determined on a percentage-of-completion basis measured by the cost-to-cost method.

From time to time, Telephonics may combine contracts if they are negotiated together, have specific requirements to combine, or are otherwise closely related. Contracts are segmented based on customer requirements.

Accounts Receivable Allowance for Doubtful Accounts and Concentrations of Credit Risk [Policy Text Block]

Accounts receivable, allowance for doubtful accounts and concentrations of credit risk

Accounts receivable is composed principally of trade accounts receivable that arise primarily from the sale of goods or services on account and is stated at historical cost. A substantial portion of Griffon’s trade receivables are from customers of HBP, of which the largest customer is Home Depot, whose financial condition is dependent on the construction and related retail sectors of the economy. In addition, a significant portion of Griffon’s trade receivables are from one Plastics customer, P&G, whose financial condition is dependent on the consumer products and related sectors of the economy. As a percentage of consolidated accounts receivable, U.S. Government related programs were 19%, P&G was 12% and Home Depot was 10%. Griffon performs continuing evaluations of the financial condition of its customers, and although Griffon generally does not require collateral, letters of credit may be required from customers in certain circumstances.

Trade receivables are recorded at the stated amount, less allowance for doubtful accounts and, when appropriate, for customer program reserves and cash discounts. The allowance represents estimated uncollectible receivables associated with potential customer defaults on contractual obligations (usually due to customers’ potential insolvency). The allowance for doubtful accounts includes amounts for certain customers where a risk of default has been specifically identified, as well as an amount for customer defaults based on a formula when it is determined the risk of some default is probable and estimable, but cannot yet be associated with specific customers. The provision related to the allowance for doubtful accounts is recorded in SG&A expenses. The Company writes-off accounts receivable when they are deemed to be uncollectible.

Customer program reserves and cash discounts are netted against accounts receivable when it is customer practice to reduce invoices for these amounts. The amount netted against accounts receivable in 2013 and 2012 was $6,556 and $8,653, respectively.

Contract Costs and Recognized Income Not Yet Billed [Policy Text Block]

Contract costs and recognized income not yet billed

Contract costs and recognized income not yet billed consists of amounts accounted for under the percentage of completion method of accounting, recoverable costs and accrued profit that cannot yet be invoiced under the terms of certain long-term contracts. Amounts will be invoiced when applicable contract terms, such as the achievement of specified milestones or product delivery, are met.

Inventory, Policy [Policy Text Block]

Inventories

Inventories, stated at the lower of cost (first-in, first-out or average) or market, include material, labor and manufacturing overhead costs.

Griffon’s businesses typically do not require inventory that is susceptible to becoming obsolete or dated. In general, Telephonics sells products in connection with programs authorized and approved under contracts awarded by the U.S. Government or agencies thereof and in accordance with customer specifications. Plastics primarily produces fabricated materials used by customers in the production of their products and these materials are produced against orders from those customers. HBP produces doors and non-powered lawn and garden tools in response to orders from customers of retailers and dealers or based on expected orders, as applicable.

Property, Plant and Equipment, Policy [Policy Text Block]

Property, plant and equipment

Property, plant and equipment includes the historical cost of land, buildings, equipment and significant improvements to existing plant and equipment. Expenditures for maintenance, repairs and minor renewals are expensed as incurred. When property or equipment is sold or otherwise disposed of, the related cost and accumulated depreciation is removed from the respective accounts and the gain or loss is recognized.

Depreciation expense, which includes amortization of assets under capital leases, was $62,911, $58,216 and $52,844 for the years ended September 30, 2013, 2012 and 2011, respectively, and was calculated on a straight-line basis over the estimated useful lives of the assets. Estimated useful lives for property, plant and equipment are as follows: buildings and building improvements, 25 to 40 years; machinery and equipment, 2 to 15 years and leasehold improvements, over the term of the lease or life of the improvement, whichever is shorter.

Capitalized interest costs included in Property, plant and equipment were $4,030, $2,975 and $2,250 for the years ended September 30, 2013, 2012 and 2011, respectively. The original cost of fully-depreciated property, plant and equipment remaining in use at September 30, 2013 was approximately $216,000.

Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived, Policy [Policy Text Block]

Goodwill and indefinite-lived intangibles

Goodwill is the excess of the acquisition cost of a business over the fair value of the identifiable net assets acquired. Goodwill is not amortized, but is subject to an annual impairment test unless during an interim period, impairment indicators, such as a significant change in the business climate, exist.

Griffon performed its annual impairment testing of goodwill as of September 30, 2013. The performance of the test involves a two-step process. The first step involves comparing the fair value of Griffon’s reporting units with the reporting unit’s carrying amount, including goodwill. Griffon generally determines the fair value of its reporting units using the income approach methodology of valuation that includes the present value of expected future cash flows. This method uses market assumptions specific to Griffon’s reporting units. If the carrying amount of a reporting unit exceeds the reporting unit’s fair value, Griffon performs the second step of the goodwill impairment test to determine the amount of impairment loss. The second step compares the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill.

Griffon defines its reporting units as its three segments.

Griffon used five year projections and a 3.0% terminal value to which discount rates between 9% and 11.25% were applied to calculate each unit’s fair value. To substantiate fair values derived from the income approach methodology of valuation, the implied fair value was reconciled to Griffon’s market capitalization, the results of which supported the implied fair values. Any changes in key assumptions or management judgment with respect to a reporting unit or its prospects, which may result from a decline in Griffon’s stock price, a change in market conditions, market trends, interest rates or other factors outside Griffon’s control, or significant underperformance relative to historical or project future operating results, could result in a significantly different estimate of the fair value of the reporting units, which could result in a future impairment charge.

Based upon the results of the annual impairment review, it was determined that the fair value of each reporting unit substantially exceeded the carrying value of the assets, as performed under step one, and no impairment existed.

Similar to goodwill, Griffon tests indefinite-lived intangible assets at least annually and when indicators of impairment exist. Griffon uses a discounted cash flow method to calculate and compare the fair value of the intangible to its book value. This method uses market assumptions specific to Griffon’s reporting units, which are reasonable and supportable. If the fair value is less than the book value of the indefinite-lived intangibles, an impairment charge would be recognized.

There was 0 impairment related to any goodwill or indefinite-lived intangible assets in 2013, 2012 or 2011.

Definite Lived Long Lived Assets [Policy Text Block]

Definite-lived long-lived assets

Amortizable intangible assets are carried at cost less accumulated amortization. For financial reporting purposes, definite-lived intangible assets are amortized on a straight-line basis over their useful lives, generally eight to twenty-five years. Long-lived assets and certain identifiable intangible assets to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition.

There were no indicators of impairment during the three years ending September 30, 2013

Income Tax, Policy [Policy Text Block]

Income taxes

Income taxes are accounted for under the liability method. Deferred taxes reflect the tax consequences on future years of differences between the tax basis of assets and liabilities and their financial reporting amounts. The carrying value of Griffon’s deferred tax assets is dependent upon Griffon’s ability to generate sufficient future taxable income in certain tax jurisdictions. Should Griffon determine that it is more likely than not that some portion of the deferred tax assets will not be realized, a valuation allowance against the deferred tax assets would be established in the period such determination was made.

Griffon provides for uncertain tax positions and any related interest and penalties based upon Management’s assessment of whether a tax benefit is more likely than not of being sustained upon examination by tax authorities. At September 30, 2013 Griffon believes that it has appropriately accounted for all unrecognized tax benefits. As of September 30, 2013, 2012 and 2011, Griffon has recorded unrecognized tax benefits in the amount of $10,520, $11,876 and $12,910, respectively. Accrued interest and penalties related to income tax matters are recorded in the provision for income taxes.

Research Development Costs Shipping and Handling Costs and Advertising Costs [Policy Text Block]

Research and development costs, shipping and handling costs and advertising costs

Research and development costs not recoverable under contractual arrangements are charged to SG&A expense as incurred and amounted to $22,400, $23,600 and $23,900 in 2013, 2012 and 2011, respectively.

Selling, general and administrative (“SG&A”) expenses include shipping and handling costs of $39,600 in 2013, $40,200 in 2012 and $41,600 in 2011 and advertising costs, which are expensed as incurred, of $23,000 in 2013, $22,000 in 2012 and $23,000 in 2011.

Risk Retention and Insurance [Policy Text Block]

Risk, retention and insurance

Griffon’s property and casualty insurance programs contain various deductibles that, based on Griffon’s experience, are reasonable and customary for a company of its size and risk profile. Griffon generally maintains deductibles for claims and liabilities related primarily to workers’ compensation, general, product and automobile liability as well as property damage and business interruption losses resulting from certain events. Griffon does not consider any of the deductibles to represent a material risk to Griffon. Griffon accrues for claim exposures that are probable of occurrence and can be reasonably estimated. Insurance is maintained to transfer risk beyond the level of self-retention and provides protection on both an individual claim and annual aggregate basis.

In the U.S., Griffon currently self-assumes its general and product liability claims up to $350 per occurrence and its workers’ compensation and automobile liability claims up to $250 per occurrence. Third-party insurance provides primary level coverage in excess of these deductible amounts up to certain specified limits. In addition, Griffon has excess liability insurance from third-party insurers on both an aggregate and an individual occurrence basis substantially in excess of the limits of the primary coverage.

Griffon has local insurance coverage in Germany, Canada, Brazil, Australia, Turkey, China, Sweden, and Mexico. Griffon has worldwide excess coverage above these local programs.

Griffon Corporation and its U.S. subsidiaries also self insures health related claims to a maximum of $300 per participant, per year.

Pension and Other Postretirement Plans, Policy [Policy Text Block]

Pension benefits

Griffon sponsors defined and supplemental benefit pension plans for certain active and retired employees. Annual amounts relating to these plans are recorded based on actuarial projections, which include various actuarial assumptions, including discount rates, assumed rates of return, compensation increases and turnover rates. The actuarial assumptions used to determine pension liabilities and assets, as well as pension expense, are reviewed on an annual basis when modifications to assumptions are made based on current economic conditions and trends. The expected return on plan assets is determined based on the nature of the plans’ investments and expectations for long-term rates of return. The discount rate used to measure obligations is based on a corporate bond spot-rate yield curve that matches projected future benefit payments with the appropriate spot rate applicable to the timing of the projected future benefit payments. The assumptions utilized in recording Griffon’s obligations under the defined benefit pension plans are believed to be reasonable based on experience and advice from independent actuaries; however, differences in actual experience or changes in the assumptions may materially affect Griffon’s financial position or results of operations.

The U.S. components of the defined benefit plans, which excludes the supplemental and post retirement healthcare and insurance benefit plans, are frozen and have ceased accruing benefits.

Newly Issued But Not Yet Effective Accounting Pronouncements [Policy Text Block]

Newly issued but not yet effective accounting pronouncements

In February 2013, the FASB issued new accounting guidance requiring enhanced disclosures for items reclassified out of accumulated other comprehensive income. The guidance does not amend any existing requirements for reporting net income or other comprehensive income in the financial statements. This guidance is effective prospectively for annual reporting periods beginning after December 15, 2012, with early adoption permitted. As this new guidance is related to presentation only, the implementation of this guidance in the first quarter of fiscal year 2014 will not have a material effect on the Company’s financial condition or results of operations.

In July 2013, the FASB issued new accounting guidance requiring an unrecognized tax benefit to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss or tax credit carryforward, except for instances when the carryforward is not available to settle any additional income taxes and an entity does not intend to use the deferred tax benefit for these purposes. In these circumstances, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. This guidance is effective for the Company beginning in 2015 and is not expected to have a material impact on the Company’s financial condition or results of operations.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently issued effective accounting pronouncements

In June 2011, the FASB issued new accounting guidance requiring the presentation of comprehensive income, the components of net income, and the components of other comprehensive income either in a single continuous statement of comprehensive income, or in two separate but consecutive statements. The new accounting rules eliminate the option to present components of other comprehensive income as part of the statement of changes in shareholders’ equity. The new accounting rules were effective for the Company beginning in 2013 and did not have a material effect on the Company’s financial condition or results of operations and the Company presented comparable financial results.

In September 2011, the FASB issued new accounting guidance that allows an entity to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative impairment testing of goodwill and indefinite life intangibles. This guidance is effective for the Company beginning in 2013 and did not have an impact on the Company’s financial condition or results of operations.

The Company has implemented all new accounting pronouncements that are in effect and that may impact its financial statements and does not believe that there are any other new accounting pronouncements that have been issued that might have a material impact on its financial position or results of operations.