Summary of Significant Accounting Policies (Policies)	6 Months Ended
Nov. 28, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements of Cal-Maine Foods, Inc. and its subsidiaries (the “Company,” “we,” “us,” “our”) have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Therefore, they do not include all of the information and footnotes required by generally accepted accounting principles in the United States of America (“GAAP”) for complete financial statements and should be read in conjunction with our Annual Report on Form 10-K for the fiscal year ended May 30, 2020, (the “2020 Annual Report”). These statements reflect all adjustments that are, in the opinion of management, necessary to a fair statement of the results for the interim periods presented and, in the opinion of management, consist of adjustments of a normal recurring nature. Operating results for the interim periods are not necessarily indicative of operating results for the entire fiscal year.
Fiscal Year	Fiscal Year The Company's fiscal year ends on the Saturday closest to May 31. Each of the three-month periods and year-to-date periods ended on November 28, 2020 and November 30, 2019 included 13 and 26 weeks, respectively.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The severity, magnitude and duration, as well as the economic consequences of the COVID-19 pandemic, are uncertain, rapidly changing and difficult to predict. Therefore, our accounting estimates and assumptions might change materially in future periods in response to COVID-19.
Trade Receivables	Trade Receivables Trade receivables are stated at their carrying value, net of a reserve for credit losses. At November 28, 2020 and May 30, 2020, reserves for credit losses were $766 thousand and $744 thousand, respectively. The Company extends credit to customers based on an evaluation of each customer’s financial condition and credit history. Collateral is generally not required. The Company minimizes exposure to counter party credit risk through credit analysis and approvals, credit limits, and monitoring procedures. In determining our reserve for credit losses, receivables are pooled according to age, with each pool assigned an expected loss percentage based on historical loss experience adjusted as needed for economic and other forward-looking factors. Accounts receivable are written off when deemed uncollectible.
Change in Accounting Principle	Change in Accounting PrincipleEffective May 31, 2020, the Company adopted ASU 2016-13, Financial Instruments – Credit Losses (“Topic 326”), which is intended to improve financial reporting by requiring more timely recording of credit losses on loans and other financial instruments. The guidance replaces the prior “incurred loss” approach with an “expected loss” model and requires measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. The Company adopted the guidance on a modified retrospective basis through a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. The Company evaluated its current methodology of estimating allowance for doubtful accounts and the risk profile of its receivables portfolio and developed a model that includes the qualitative and forecasting aspects of the “expected loss” model under the amended guidance. The Company finalized its assessment of the impact of the amended guidance and recorded a $422 thousand cumulative increase to retained earnings at May 31, 2020.
Investment, Policy	Investment SecuritiesOur investment securities are accounted for in accordance with ASC 320, “Investments - Debt and Equity Securities” (“ASC 320”). The Company considers all of its debt securities for which there is a determinable fair market value, and there are no restrictions on the Company's ability to sell within the next 12 months, as available-for-sale. We classify these securities as current, because the amounts invested are available for current operations. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported as a separate component of stockholders’ equity. The Company regularly evaluates changes to the rating of its debt securities by credit agencies and economic conditions to assess and record any expected credit losses through allowance for credit losses limited to the amount that fair value was less than the amortized cost basis. The cost basis for realized gains and losses on available-for-sale securities is determined on the specific identification method. Gains and losses are recognized in other income (expenses) as Other, net in the Company's Condensed Consolidated Statements of Operations. Investments in mutual funds are classified as “Other long-term assets” in the Company’s Consolidated Balance Sheets.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Nov. 28, 2020

The unaudited condensed consolidated financial statements of Cal-Maine Foods, Inc. and its subsidiaries (the “Company,” “we,” “us,” “our”) have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Therefore, they do not include all of the information and footnotes required by generally accepted accounting principles in the United States of America (“GAAP”) for complete financial statements and should be read in conjunction with our Annual Report on Form 10-K for the fiscal year ended May 30, 2020, (the “2020 Annual Report”). These statements reflect all adjustments that are, in the opinion of management, necessary to a fair statement of the results for the interim periods presented and, in the opinion of management, consist of adjustments of a normal recurring nature. Operating results for the interim periods are not necessarily indicative of operating results for the entire fiscal year.

Fiscal Year

The Company's fiscal year ends on the Saturday closest to May 31. Each of the three-month periods and year-to-date periods ended on November 28, 2020 and November 30, 2019 included 13 and 26 weeks, respectively.

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.

The severity, magnitude and duration, as well as the economic consequences of the COVID-19 pandemic, are uncertain, rapidly changing and difficult to predict. Therefore, our accounting estimates and assumptions might change materially in future periods in response to COVID-19.

Trade Receivables

Trade receivables are stated at their carrying value, net of a reserve for credit losses. At November 28, 2020 and May 30, 2020, reserves for credit losses were $766 thousand and $744 thousand, respectively. The Company extends credit to customers based on an evaluation of each customer’s financial condition and credit history. Collateral is generally not required. The Company minimizes exposure to counter party credit risk through credit analysis and approvals, credit limits, and monitoring procedures. In determining our reserve for credit losses, receivables are pooled according to age, with each pool assigned an expected loss percentage based on historical loss experience adjusted as needed for economic and other forward-looking factors. Accounts receivable are written off when deemed uncollectible.

Change in Accounting Principle

Change in Accounting PrincipleEffective May 31, 2020, the Company adopted ASU 2016-13, Financial Instruments – Credit Losses (“Topic 326”), which is intended to improve financial reporting by requiring more timely recording of credit losses on loans and other financial instruments. The guidance replaces the prior “incurred loss” approach with an “expected loss” model and requires measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. The Company adopted the guidance on a modified retrospective basis through a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. The Company evaluated its current methodology of estimating allowance for doubtful accounts and the risk profile of its receivables portfolio and developed a model that includes the qualitative and forecasting aspects of the “expected loss” model under the amended guidance. The Company finalized its assessment of the impact of the amended guidance and recorded a $422 thousand cumulative increase to retained earnings at May 31, 2020.

Investment, Policy

Investment SecuritiesOur investment securities are accounted for in accordance with ASC 320, “Investments - Debt and Equity Securities” (“ASC 320”). The Company considers all of its debt securities for which there is a determinable fair market value, and there are no restrictions on the Company's ability to sell within the next 12 months, as available-for-sale. We classify these securities as current, because the amounts invested are available for current operations. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported as a separate component of stockholders’ equity. The Company regularly evaluates changes to the rating of its debt securities by credit agencies and economic conditions to assess and record any expected credit losses through allowance for credit losses limited to the amount that fair value was less than the amortized cost basis. The cost basis for realized gains and losses on available-for-sale securities is determined on the specific identification method. Gains and losses are recognized in other income (expenses) as Other, net in the Company's Condensed Consolidated Statements of Operations. Investments in mutual funds are classified as “Other long-term assets” in the Company’s Consolidated Balance Sheets.