Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Nov. 30, 2016
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation Griffin Industrial Realty, Inc. (“Griffin”) is a real estate business principally engaged in developing, managing and leasing industrial and commercial properties. Griffin also seeks to add to its property portfolio through the acquisition and development of land or purchase of buildings. Periodically, Griffin may sell certain portions of its undeveloped land that it has owned for an extended time period and the use of which is not consistent with Griffin’s core development and leasing strategy. Prior to May 13, 2015, Griffin was known as Griffin Land & Nurseries, Inc. Griffin changed its name to better reflect its ongoing real estate business after the sale in fiscal 2014 of the landscape nursery business that Griffin had operated through its wholly owned subsidiary, Imperial Nurseries, Inc. (“Imperial”). Imperial was engaged in growing landscape nursery plants in containers for sale to independent retail garden centers and rewholesalers, whose main customers are landscape contractors. Imperial's operations through January 8, 2014 are reflected in the accompanying consolidated financial statements as a discontinued operation due to the sale of its inventory and certain of its assets (the “Imperial Sale”) to Monrovia Connecticut LLC (“Monrovia”), a subsidiary of Monrovia Nursery Company (see Note 10). All intercompany transactions have been eliminated.
Fiscal Year	Fiscal Year Griffin reports on a twelve month fiscal year that ends on November 30.
Real Estate Assets	Real Estate Assets Real estate assets are recorded at cost, except when real estate assets are acquired that meet the definition of a business combination in accordance with Financial Accounting Standards Board (“FASB”) ASC 805-10, “Business Combinations,” and are recorded at fair value. Interest, property taxes, insurance and other incremental costs (including salaries) directly related to a project are capitalized during the construction period of major facilities and land improvements. The capitalization period begins when activities to develop the parcel commence and ends when the asset constructed is completed. The capitalized costs are recorded as part of the asset to which they relate and are amortized over the asset's useful life. Depreciation is determined on a straight-line basis over the estimated useful asset lives for financial reporting purposes and principally on accelerated methods for tax purposes. Repair and maintenance costs are expensed as incurred. Griffin classifies a property as “held for sale” when all of the following criteria for a plan of sale have been met: (1) management, having the authority to approve the action, commits to a plan to sell the property; (2) the property is available for immediate sale in its present condition, subject only to terms that are usual and customary; (3) an active program to locate a buyer and other actions required to complete the plan to sell, have been initiated; (4) the sale of the property is probable and is expected to be completed within one year or the property is under a contract to be sold; (5) the property is being actively marketed for sale at a price that is reasonable in relation to its current fair value; and (6) actions necessary to complete the plan of sale indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn. When all of these criteria have been met, the property is classified as “held for sale.” Depreciation of assets ceases upon designation of a property as “held for sale.”
Cash and Cash Equivalents	Cash and Cash Equivalents Griffin considers all highly liquid investments with an initial maturity of three months or less at the date of purchase to be cash equivalents. At November 30, 2016 and 2015, $22,409 and $15,269, respectively, of the cash and cash equivalents included on Griffin's consolidated balance sheets were held in cash equivalents.
Investments	Investments Griffin's investment in the common stock of Centaur Media plc (“Centaur Media”) is accounted for as an available-for-sale security under FASB ASC 320-10, “Investments – Debt and Equity Securities” (“ASC 320-10”), whereby increases or decreases in the fair value of this investment, net of income taxes, along with the effect of changes in the foreign currency exchange rate, net of income taxes, are recorded as a component of other comprehensive income (loss). Realized gains and losses on sales of available-for-sale securities are determined based on the average cost method. Griffin is required to adopt FASB Accounting Standards Update No. 2016-01, “Financial Instruments – Overall” (“ASU 2016-01”) in fiscal 2019. Upon adoption, the increases or decreases in the fair value of available-for-sale securities will no longer be reflected as a component of other comprehensive income, but will be recognized through net income (see Recent Accounting Pronouncements below).
Stock-Based Compensation	Stock‑Based Compensation Griffin accounts for stock options at fair value in accordance with FASB ASC 718, “Compensation - Stock Compensation” and FASB ASC 505-50, “Equity – Equity-Based Payments to Non-Employees.” For stock options that have graded vesting features, Griffin recognizes compensation cost over the requisite service period separately for each tranche of the award as though they were, in substance, multiple awards. Griffin determines its accumulated windfall tax benefits using the short-cut method.
Postretirement Benefits	Postretirement Benefits In fiscal 2014, Griffin terminated its postretirement benefit program (see Note 7). Griffin had accounted for postretirement benefits in accordance with FASB ASC 715-10, “Compensation – Retirement Benefits” (“ASC 715-10”). This guidance requires an employer to recognize the overfunded or underfunded status of a defined benefit postretirement plan (other than a multiemployer plan) as an asset or liability in its statement of financial position and to recognize changes in that funded status in the year in which the changes occur through other comprehensive income. This guidance also requires an employer to measure the funded status of a plan as of the date of its year-end statement of financial position, with limited exceptions.
Impairment of Investments in Long-Lived Assets	Impairment of Investments in Long‑Lived Assets Griffin reviews annually, as well as when conditions may indicate, its long-lived assets to determine if there are indicators of impairment, such as a prolonged vacancy in one of its properties. If indicators of impairment are present, Griffin evaluates the carrying value of the assets in relation to the operating performance and expected future undiscounted cash flows or the estimated fair value based on expected future cash flows of the underlying assets. If the undiscounted cash flows are less than the carrying value of an asset, Griffin would reduce the carrying value of a long-lived asset to its fair value if that asset’s fair value is determined to be less than its carrying value. Griffin also reviews annually, as well as when conditions may indicate, the recoverability of its development costs, including expected remediation costs on projects that are included in real estate assets. To the extent that the carrying value exceeds the fair value of a project, including development costs, an impairment loss would be recorded. There were no impairment losses recorded in the fiscal years ended November 30, 2016, 2015 and 2014.
Revenue and Gain Recognition	Revenue and Gain Recognition Revenue includes rental revenue from Griffin's industrial and commercial properties and proceeds from property sales. Rental revenue is accounted for on a straight line basis over the applicable lease term in accordance with FASB ASC 840-10, “Leases.” Gains on property sales are recognized in accordance with FASB ASC 360-20, “Property, Plant, and Equipment – Real Estate Sales,” based on the specific terms of each sale. When the percentage of completion method is used to account for a sale of real estate, costs included in determining the percentage of completion include the costs of the land sold, allocated master planning costs, selling and transaction costs and estimated future costs related to the land sold. The growing operations of the landscape nursery business are reflected as a discontinued operation in the consolidated statements of operations.
Income Taxes	Income Taxes Griffin provides for income taxes utilizing the asset and liability method, and records deferred tax assets and liabilities based on the difference between the financial statement and tax bases of assets and liabilities as measured by the tax rates that are anticipated to be in effect when these differences reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the results of operations in the period that includes the enactment date. A valuation allowance is established when it is necessary to reduce deferred tax assets to amounts for which realization is more likely than not. Griffin and its subsidiaries file a consolidated federal income tax return. Griffin evaluates each tax position taken in its tax returns and recognizes a liability for any tax position deemed less likely than not to be sustained under examination by the relevant taxing authorities. Griffin has analyzed its federal and significant state filing positions with respect to FASB ASC 740-10, “Income Taxes” (“ASC 740-10”). Griffin believes that its income tax filing positions will be sustained on examination and does not anticipate any adjustments that would result in a material change on its financial statements. As a result, no accrual for uncertain income tax positions has been recorded pursuant to ASC 740-10. Griffin’s policy for recording interest and penalties, related to uncertain tax positions, is to record such items as part of its provision for federal and state income taxes.
Intangible Assets	Intangible Assets Griffin accounts for intangible assets in accordance with FASB ASC 350-10 “Intangibles - Goodwill and Other.” Griffin's intangible assets consist of: (i) the value of in-place leases; and (ii) the value of the associated relationships with tenants. These intangible assets were recorded in connection with Griffin’s acquisitions of real estate assets. Amortization of the value of in-place leases, included in depreciation and amortization expense, is on a straight-line basis over the lease terms. Amortization of the value of customer relationships with tenants, included in depreciation and amortization expense, is on a straight-line basis over the lease terms and anticipated renewal periods.
Environmental Matters	Environmental Matters Environmental expenditures related to land and buildings are expensed or capitalized as appropriate, depending upon their future economic benefit. Expenditures that relate to an existing condition caused by past operations, and that do not have future economic benefit, are expensed. Expenditures that create future benefit or contribute to future revenue generation are capitalized. Liabilities related to future remediation costs are recorded when environmental assessments and/or cleanups are probable, and the costs can be reasonably estimated.
Interest Rate Swap Agreements	Interest Rate Swap Agreements As of November 30, 2016, Griffin was a party to several interest rate swap agreements to hedge its interest rate exposures. Griffin does not use derivatives for speculative purposes. Griffin applies FASB ASC 815-10, “Derivatives and Hedging,” (“ASC 815-10”) as amended, which establishes accounting and reporting standards for derivative instruments and hedging activities. ASC 815-10 requires Griffin to recognize all derivatives as either assets or liabilities on its consolidated balance sheet and measure those instruments at fair value. The changes in the fair values of the interest rate swap agreements are measured in accordance with ASC 815-10 and reflected in the carrying values of the interest rate swap agreements on Griffin’s consolidated balance sheet. The estimated fair values are based primarily on projected future swap rates. Griffin applies cash flow hedge accounting to its interest rate swap agreements that are designated as hedges of the variability of future cash flows from floating rate liabilities based on benchmark interest rates. The changes in fair values of Griffin’s interest rate swap agreements are recorded as components of accumulated other comprehensive income (loss) (“AOCI”) in stockholders’ equity, to the extent they are effective. Any ineffective portions of the changes in fair values of these instruments would be recorded as interest expense or interest income.
Conditional Asset Retirement Obligations	Conditional Asset Retirement Obligations Griffin accounts for its conditional asset retirement obligations in accordance with FASB ASC 410-10, “Asset Retirement and Environmental Obligations,” which requires an entity to recognize a liability for the fair value of a conditional asset retirement obligation if the fair value can be reasonably estimated even though uncertainty exists about the timing and/or method of settlement. The conditional asset retirement obligations relate principally to tobacco barns and other structures on Griffin’s land holdings that contain asbestos, primarily in roofing materials. These structures remain from the tobacco growing operations of former affiliates of Griffin, are not material to Griffin’s operations and do not have any book value.
Treasury Stock	Treasury Stock Treasury stock is recorded at cost as a reduction of stockholders’ equity on Griffin’s consolidated balance sheets.
Income (Loss) Per Share	Income (Loss) Per Share Basic income (loss) per common share is calculated by dividing income (loss) from continuing operations and discontinued operations by the weighted average number of common shares outstanding during the year. The calculation of diluted income (loss) per common share reflects adjusting Griffin’s outstanding shares assuming the exercise of all potentially dilutive Griffin stock options.
Risks and Uncertainties	Risks and Uncertainties Griffin’s future results of operations involve a number of risks and uncertainties. Factors that could affect Griffin’s future operating results and cause actual results to vary materially from historical results include, but are not limited to, the geographical concentration of Griffin’s real estate holdings, credit risk and market risk. Griffin's real estate holdings are concentrated in the Hartford, Connecticut area and in the Lehigh Valley of Pennsylvania. The market and economic challenges experienced by the U.S. economy as a whole or the local economic conditions in the markets in which Griffin holds properties may affect Griffin’s real estate business. Griffin’s results of operations, financial condition or ability to expand may be adversely affected as a result of: (i) poor economic conditions or unfavorable financial changes to Griffin’s tenants, which may lead to a curtailment of expansion plans or may result in tenant defaults under leases; (ii) significant job losses, which could adversely affect the demand for rental space causing market rental rates and property values to be negatively impacted; (iii) the ability of Griffin to borrow on terms and conditions that it finds acceptable; and (iv) possibly reduced values of Griffin’s properties potentially limiting the proceeds from a sale of its properties or from debt financing collateralized by its properties. Griffin conducts business based on evaluations of its prospective tenants’ financial condition and generally does not require collateral. These evaluations require significant judgment and are based on multiple sources of information. Griffin does not use derivatives for speculative purposes. Griffin applies ASC 815-10, which established accounting and reporting standards for derivative instruments and hedging activities. This accounting guidance requires Griffin to recognize all derivatives as either assets or liabilities on its consolidated balance sheet and to measure those instruments at fair value. The estimated fair value is based primarily on projected future swap rates. Griffin applies cash flow hedge accounting to its interest rate swap agreements designated as hedges of the variability of future cash flows from floating rate liabilities due to the benchmark interest rates. Changes in the fair value of these interest rate swaps are recorded as a component of AOCI in stockholders’ equity, to the extent they are effective. Amounts recorded to AOCI are then reclassified to interest expense as interest on the hedged borrowing is recognized. Any ineffective portion of the change in fair value of these instruments would be recorded to interest expense. Griffin’s cash equivalents consist of overnight investments that are not significantly exposed to interest rate risk.
Reclassifications	Reclassifications Certain prior year balances have been reclassified to conform to the current year’s presentation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amount of assets and liabilities and disclosure of contingent assets and liabilities at the dates of the financial statements and revenue and expenses during the periods reported. Actual results could differ from those estimates. Griffin’s significant estimates include the impairment evaluation of long-lived assets, deferred income taxes, derivative financial instruments, revenue and gain recognition including the estimated costs to complete required offsite improvements related to land sold and assumptions used in determining stock compensation.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2016, the FASB issued Accounting Standards Update No. 2016-09, “Compensation – Stock Compensation: Improvements to Employee Share-Based Payment Accounting,” which relates to the accounting for employee share-based payments. This Update addresses several aspects of the accounting for share-based payment award transactions, including: (a) income tax consequences; (b) classification of awards as either equity or liabilities; and (c) classification on the statement of cash flows. This Update will become effective for Griffin in fiscal 2018. Early adoption is allowed, but all of the guidance must be adopted in the same period. Griffin is evaluating the impact that the application of this Update will have on its consolidated financial statements. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, “Leases,” which establishes a right-of-use (“ROU”) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than twelve months. The accounting applied by lessors under this Update is largely unchanged from that applied under current U.S. GAAP. Leases will be either classified as finance or operating, with classification affecting the pattern of expense recognition in the income statement. This Update also requires significant additional disclosures about the amount, timing and uncertainty of cash flows from leases. This Update will become effective for Griffin in fiscal 2020 using a modified restatement approach for leases in effect as of and after the date of adoption. Early adoption and practical expedients to measure the effect of adoption will also be allowed. Griffin is evaluating the impact that the application of this Update will have on its consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, “Financial Instruments - Overall,” which requires all equity investments to be measured at fair value with changes in the fair value recognized through net income (other than those accounted for under the equity method of accounting or those that result in consolidation of the investee). ASU 2016-01 also requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. ASU 2016-01 eliminates the requirement for an entity to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet for public business entities. In addition, entities must assess the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets. ASU 2016-01 will be effective for Griffin in fiscal 2019. Early adoption is permitted for certain provisions. Upon adoption, changes in the fair value of Griffin’s available-for-sale securities will be recognized through net income. In April 2015, the FASB issued Accounting Standards Update No. 2015-03, “Interest-Imputation of Interest,” (“ASU 2015-03”) which requires that debt issuance costs related to a recognized liability be presented on the balance sheet as a direct reduction from the carrying amount of the associated debt liability, consistent with debt discounts. The guidance must be applied on a retrospective basis and was adopted by Griffin in the fiscal 2016 fourth quarter. The adoption of this guidance required Griffin to reclassify its debt issuance costs on nonrecourse mortgage loans from other assets to mortgage debt on its statement of financial position but did not have an impact on Griffin's results of operations. The effect of the reclassification on Griffin’s statement of financial position is quantified in Note 5. In August 2015, the FASB issued Accounting Standards Update No. 2015-15, “Interest-Imputation of Interest: Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements - Amendments to SEC Paragraphs Pursuant to Staff Announcement at June 18, 2015 EITF Meeting,” which addresses line-of-credit arrangements that were omitted from ASU 2015-03 (see above). This Update states that the SEC staff would not object to an entity deferring and presenting debt issuance costs related to a line-of-credit arrangement as an asset and subsequently amortizing those costs ratably over the term of the arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. Griffin adopted this Update in the 2016 fourth quarter. The adoption of this guidance did not have an impact on Griffin's consolidated financial statements. In May 2014, the FASB issued Accounting Standards Update No. 2014-09, “Revenue from Contracts with Customers,” which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry specific guidance. This standard requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. Additionally, the Update requires improved disclosures to help users of financial statements better understand the nature, amount, timing and uncertainty of revenue that is recognized. The Update permits the use of either the retrospective or cumulative effect transition method. This Update will be effective for Griffin in fiscal 2019 and early adoption is not permitted. Certain aspects of this new standard may affect revenue recognition of Griffin. Griffin is evaluating the impact that the application of this Update will have on its consolidated financial statements.