Note 1 - Significant Accounting Policies	3 Months Ended
Mar. 31, 2021
Notes to Financial Statements
Significant Accounting Policies [Text Block]	1. Significant Accounting Policies *Basis of Presentation* In these notes, the terms “Corning,” “Company,” “we,” “us,” or “our” mean Corning Incorporated and its subsidiary companies. The accompanying unaudited consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) and in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) for interim financial information. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been omitted or condensed. These interim consolidated financial statements should be read in conjunction with Corning’s consolidated financial statements and notes thereto included in its Annual Report on Form 10-K for the year ended December 31, 2020 (“2020 Form 10-K”). The unaudited consolidated financial statements reflect all adjustments which, in the opinion of management, are necessary for a fair statement of the results of operations, financial position and cash flows for the interim periods presented. All such adjustments are of a normal recurring nature. The results for interim periods are not necessarily indicative of results which may be expected for any other interim period or for the full year. The equity method of accounting is used for investments in affiliated companies that are not controlled by Corning and in which the Company’s interest is generally between 20% and 50% and we have significant influence over the entity. On September 9, 2020, Hemlock Semiconductor Group (“HSG”) redeemed Dupont’s entire ownership of HSG with a value of $250 million ("Redemption"). Upon completion of the Redemption, the Company obtained a 100% interest in Hemlock Semiconductor LLC and 80.5% interest in Hemlock Semiconductor Operations LLC, which are affiliated entities within HSG. HSG's results have been consolidated in “All Other”. Refer to Note 3 (HSG Transactions) to the consolidated financial statements for more information. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. The novel coronavirus (“COVID-19”) pandemic and the resulting adverse impacts to global economic conditions may impact future estimates including, but not limited to, inventory valuations, fair value measurements, goodwill and long-lived asset impairments, the effectiveness of the Company’s hedging instruments, deferred tax valuation allowances, actuarial losses on retirement benefit plans and discount rate assumptions. Certain prior year amounts have been reclassified to conform to the current-year presentation. These reclassifications had no impact on the results of operations, financial position, or changes in shareholders’ equity. *New Accounting Standards* During the first quarter of 2021, we early adopted the ASU 2020-06. The ASU simplifies an issuer’s accounting for convertible instruments by eliminating separate accounting for beneficial conversion and cash conversion features under ASC 470-20. The ASU also clarifies the settlement assessment that entities are required to perform to determine whether a contract qualifies for equity classification under ASC 815-40, as well as requires entities to use the if-converted method for all convertible instruments in the diluted EPS calculation and include the effect of potential share settlement, if the effect is more dilutive, for instruments that may be settled in cash or shares under ASC 260. The adoption of ASU 2020-06 did not have a one-time impact on Corning’s consolidated financial statements as of January 1, 2021.

Note 1 - Significant Accounting Policies

3 Months Ended

Mar. 31, 2021

Significant Accounting Policies [Text Block]

1. Significant Accounting Policies

Basis of Presentation

In these notes, the terms “Corning,” “Company,” “we,” “us,” or “our” mean Corning Incorporated and its subsidiary companies.

The accompanying unaudited consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) and in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”) for interim financial information. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been omitted or condensed. These interim consolidated financial statements should be read in conjunction with Corning’s consolidated financial statements and notes thereto included in its Annual Report on Form 10-K for the year ended December 31, 2020 (“2020 Form 10-K”).

The unaudited consolidated financial statements reflect all adjustments which, in the opinion of management, are necessary for a fair statement of the results of operations, financial position and cash flows for the interim periods presented. All such adjustments are of a normal recurring nature. The results for interim periods are not necessarily indicative of results which may be expected for any other interim period or for the full year.

The equity method of accounting is used for investments in affiliated companies that are not controlled by Corning and in which the Company’s interest is generally between 20% and 50% and we have significant influence over the entity.

On September 9, 2020, Hemlock Semiconductor Group (“HSG”) redeemed Dupont’s entire ownership of HSG with a value of $250 million ("Redemption"). Upon completion of the Redemption, the Company obtained a 100% interest in Hemlock Semiconductor LLC and 80.5% interest in Hemlock Semiconductor Operations LLC, which are affiliated entities within HSG. HSG's results have been consolidated in “All Other”.

Refer to Note 3 (HSG Transactions) to the consolidated financial statements for more information.

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. The novel coronavirus (“COVID-19”) pandemic and the resulting adverse impacts to global economic conditions may impact future estimates including, but not limited to, inventory valuations, fair value measurements, goodwill and long-lived asset impairments, the effectiveness of the Company’s hedging instruments, deferred tax valuation allowances, actuarial losses on retirement benefit plans and discount rate assumptions.

Certain prior year amounts have been reclassified to conform to the current-year presentation. These reclassifications had no impact on the results of operations, financial position, or changes in shareholders’ equity.

New Accounting Standards

During the first quarter of 2021, we early adopted the ASU 2020-06. The ASU simplifies an issuer’s accounting for convertible instruments by eliminating separate accounting for beneficial conversion and cash conversion features under ASC 470-20. The ASU also clarifies the settlement assessment that entities are required to perform to determine whether a contract qualifies for equity classification under ASC 815-40, as well as requires entities to use the if-converted method for all convertible instruments in the diluted EPS calculation and include the effect of potential share settlement, if the effect is more dilutive, for instruments that may be settled in cash or shares under ASC 260. The adoption of ASU 2020-06 did not have a one-time impact on Corning’s consolidated financial statements as of January 1, 2021.