FAIR VALUE MEASUREMENTS	6 Months Ended
FAIR VALUE MEASUREMENTS	Mar. 31, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The carrying values of cash and equivalents, accounts receivable, accounts and notes payable, and revolving credit and variable interest rate 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 and variable rate debt is based upon current market rates. Applicable accounting guidance establishes a fair value hierarchy requiring the Company to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s categorization within the hierarchy is based on the lowest level of input that is significant to the fair value measurement. The accounting guidance establishes three levels of inputs that may be used to measure fair value, as follows: •Level 1 inputs are measured and recorded at fair value based upon quoted prices in active markets for identical assets. •Level 2 inputs include inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of assets or liabilities. •Level 3 inputs are unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. The fair values of Griffon’s 2028 senior notes approximated $1,060,000 on March 31, 2021. Fair values were based upon quoted market prices (level 1 inputs). Insurance contracts with values of $3,821 at March 31, 2021 are measured and recorded at fair value based upon quoted prices in active markets for similar assets (level 2 inputs) and are included in Prepaid and other current assets on the Consolidated Balance Sheets. Items Measured at Fair Value on a Recurring Basis At March 31, 2021, trading securities, measured at fair value based on quoted prices in active markets for similar assets (level 2 inputs), with a fair value of $2,088 ($1,000 cost basis), were included in Prepaid and other current assets on the Consolidated Balance Sheets. Realized and unrealized gains and losses on trading securities are included in Other income in the Consolidated Statements of Operations and Comprehensive Income (Loss). In the normal course of business, Griffon’s operations are exposed to the effects of changes in foreign currency exchange rates. To manage these risks, Griffon may enter into various derivative contracts such as foreign currency exchange contracts, including forwards and options. As of March 31, 2021, Griffon entered into several such contracts in order to lock into a foreign currency rate for planned settlements of trade and inter-company liabilities payable in US dollars. At March 31, 2021, Griffon had $61,000 of Australian dollar contracts at a weighted average rate of $1.29 which qualified for hedge accounting (level 2 inputs). These hedges were all deemed effective as cash flow hedges with gains and losses related to changes in fair value deferred and recorded in Accumulated other comprehensive income (loss) ("AOCI") and Prepaid and other current assets, or Accrued liabilities, until settlement. Upon settlement, gains and losses are recognized in the Consolidated Statements of Operations and Comprehensive Income (Loss) in Cost of goods and services ("COGS"). AOCI included deferred losses of $831 ($582, net of tax) at March 31, 2021. Upon settlement, losses of $1,741 and $2,399 were recorded in COGS during the three and six months ended March 31, 2021, respectively. All contracts expire in 30 to 180 days. At March 31, 2021, Griffon had $7,935 of Canadian dollar contracts at a weighted average rate of $1.30. The contracts, which protect Canadian operations from currency fluctuations for US dollar based purchases, do not qualify for hedge accounting. For the three and six months ended March 31, 2021, fair value gains of $520 and $244, respectively, were recorded to Other liabilities and to Other income for the outstanding contracts, based on similar contract values (level 2 inputs). Realized losses of $102 and $161 were recorded in Other income during the three and six months ended March 31, 2021, respectively, for all settled contracts. All contracts expire in 29 to 450 days. At March 31, 2021, Griffon had $5,200 of British Pound dollar contracts at a weighted average rate of $0.75. The contracts, which protect United Kingdom operations from currency fluctuations for US dollar based purchases, do not qualify for hedge accounting. For the three and six months ended March 31, 2021, fair value gains of $386 and $141, respectively, were recorded to Other assets and to Other income for the outstanding contracts, based on similar contract values (level 2 inputs). Realized losses of $211 and $281 were recorded in Other income during the three and six months ended March 31, 2021, respectively. All contracts expire in 6 to 104 days.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.