BASIS OF FINANCIAL STATEMENT PRESENTATION	3 Months Ended
Sep. 30, 2020
Accounting Policies [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block]	BASIS OF FINANCIAL STATEMENT PRESENTATION Laboratory Corporation of America® Holdings together with its subsidiaries (the Company) is a leading global life sciences company that is deeply integrated in guiding patient care, providing comprehensive clinical laboratory and end-to-end drug development services. The Company’s mission is to improve health and improve lives by delivering world-class diagnostic solutions, bringing innovative medicines to patients faster and using technology to provide better care. The Company serves a broad range of customers, including managed care organizations (MCOs), biopharmaceutical and medical device companies, governmental agencies, physicians and other health care providers (e.g., physician assistants and nurse practitioners, generally referred to herein as physicians), hospitals and health systems, employers, patients and consumers, contract research organizations (CROs), and independent clinical laboratories. The Company reports its business in two segments, LabCorp Diagnostics (LCD) and Covance Drug Development (CDD). For further financial information about these segments, see Note 15 Business Segment Information to the Condensed Consolidated Financial Statements. During the three months ended September 30, 2020, LCD and CDD contributed approximately 68% and 32% respectively, of revenues to the Company. During the nine months ended September 30, 2020, LCD and CDD contributed approximately 63% and 37%, respectively, of revenues to the Company. The condensed consolidated financial statements include the accounts of the Company and its majority-owned subsidiaries for which it exercises control. Long-term investments in affiliated companies in which the Company exercises significant influence, but which it does not control, are accounted for using the equity method. Investments in which the Company does not exercise significant influence (generally, when the Company has an investment of less than 20.0% and no representation on the investee's board of directors) are accounted for at fair value or at cost minus impairment adjusted for observable price changes in orderly transactions for an identical or similar investment of the same issuer for those investments that do not have readily determinable fair values. All significant inter-company transactions and accounts have been eliminated. The Company does not have any significant variable interest entities or special purpose entities whose financial results are not included in the condensed consolidated financial statements. The financial statements of the Company's operating foreign subsidiaries are measured using the local currency as the functional currency. Assets and liabilities are translated at exchange rates as of the balance sheet date. Revenues and expenses are translated at average monthly exchange rates prevailing during the period. Resulting translation adjustments are included in “Accumulated other comprehensive income.” The accompanying condensed consolidated financial statements of the Company are unaudited. In the opinion of management, all adjustments necessary for a fair statement of results of operations, cash flows, and financial position have been made. Except as otherwise disclosed, all such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for a full year. The year-end condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by generally accepted accounting principles. The condensed consolidated financial statements and notes are presented in accordance with the rules and regulations of the United States (U.S.) Securities and Exchange Commission (SEC) and do not contain certain information included in the Company’s 2019 Annual Report on Form 10-K (Annual Report). Therefore, these interim statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report. Recently Adopted Guidance In June 2016, the FASB issued a new accounting standard intended to provide financial statement users with more decision-useful information about expected credit losses and other commitments to extend credit held by the reporting entity. The standard replaces the incurred loss impairment methodology in current generally accepted accounting principles (GAAP) with one that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The Company recorded an opening retained earnings adjustment of $7.0 with the adoption of this standard on January 1, 2020. In August 2018, the FASB issued a new accounting standard to reduce, modify, and add to the disclosure requirements on fair value measurements. The Company adopted this standard effective January 1, 2020. The adoption of this standard did not have a material impact on the consolidated financial statements. In August 2018, the FASB issued a new accounting standard to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The Company adopted this standard effective January 1, 2020. The adoption of this standard did not have a material impact on the consolidated financial statements. New Accounting Pronouncements In August 2018, the FASB issued a new accounting standard to reduce, modify, and add to the disclosure requirements on defined benefit pension and other postretirement plans. The standard is effective on January 1, 2021, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the consolidated financial statements. In December 2019, the FASB issued a new accounting standard to simplify accounting for income taxes and remove, modify, and add to the disclosure requirements of income taxes. The standard is effective January 1, 2021, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the consolidated financial statements. In January 2020, the FASB issued a new accounting standard to clarify the interaction of the accounting for equity securities and investments accounted for under the equity method of accounting and the accounting for certain forward contracts and purchased options. The standard is effective January 1, 2021. The adoption of this standard is not expected to have a material impact on the consolidated financial statements. In March 2020, the FASB issued a new accounting standard to provide optional expedients and exceptions if certain conditions are met for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The expedients and exceptions in the standard are effective between March 12, 2020, and December 31, 2022. The Company did not elect to apply any of the expedients or exceptions for the period ended September 30, 2020, and is currently evaluating the impact this new standard will have on the consolidated financial statements. In August 2020, the FASB issued a new accounting standard to address issues identified as a result of the complexity associated with applying generally accepted accounting principles for convertible instruments and contracts in an entity's own equity. The standard is effective January 1, 2022, with early adoption permitted. The Company is evaluating the impact this new standard will have on the consolidated financial statements. Novel Coronavirus (COVID-19) Financial Statement Impact In March 2020, COVID-19 was declared a pandemic. COVID-19 has had and continues to have an extensive impact on the global health and economic environments. During the nine months ended September 30, 2020, the Company recorded goodwill and other asset impairment charges of $437.4, as a result of the negative financial impact of COVID-19 during the first quarter of 2020. See Note 6 Goodwill and Intangible Assets for a discussion of goodwill and intangible asset impairment and Note 2 Revenues for a discussion of credit losses and additional price concessions. The Company also impaired certain of the Company's investments by a total of $25.4 during the nine months ended September 30, 2020, due to the impact of COVID-19; $7.1 was included in Equity method earnings (loss), net during the three months ended March 31, 2020, and $13.1 and $5.2 were included in Other, net during the three months ended March 31, 2020, and June 30, 2020, respectively. In April 2020, the Company received cash payments of approximately $55.9 from the Public Health and Social Services Emergency Fund for provider relief that was appropriated by Congress to the Department of Health and Human Services (HHS) in the Coronavirus Aid, Relief, and Economic Security Act (CARES Act Provider Relief Funds). Upon receiving and satisfying the terms and conditions associated with the distributed funds, the Company accounted for the transaction by applying the guidance in ASC 450-30 Gain Contingencies, and recorded these funds in Other, net non-operating income in the Consolidated Statement of Operations as of June 30, 2020. In August 2020, the Company received an additional $76.2 in CARES Act Provider Relief Funds. As the Company's Diagnostic business demonstrated recovery and demand for COVID-19 testing increased, the Company determined that the negative financial impact of COVID-19 which the CARES Act Provider Relief Funds were designed to address no longer applied to the Company. As a result, the Company derecognized the income associated with the $55.9 received during the second quarter as a change in estimate and did not recognize any income related to the cash payment of $76.2 received in the third quarter. The Company plans to return the CARES Act Provider Relief Funds to the government in the fourth quarter of 2020 and has recorded a liability of $132.1 in Accrued expenses and other as of September 30, 2020. Use of Estimates The extent to which the COVID-19 pandemic has and will impact the Company’s business and financial results depend on numerous evolving factors including, but not limited to: the magnitude and duration of the COVID-19 pandemic, the impact to worldwide macroeconomic conditions including interest rates, employment rates and health insurance coverage, the speed of the anticipated recovery, and governmental and business reactions to the pandemic. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to the Company and the unknown future impacts of COVID-19 as of September 30, 2020, and through the date of this report. The accounting matters assessed included, but were not limited to, the Company’s implicit price concessions and credit losses, equity investments, notes receivable and the carrying value of goodwill and other long-lived assets. The Company’s future assessment of the magnitude and duration of COVID-19, as well as other factors, could result in additional material impacts to the Company’s consolidated financial statements in future reporting periods.
Basis of Presentation and Significant Accounting Policies [Text Block]	BASIS OF FINANCIAL STATEMENT PRESENTATION Laboratory Corporation of America® Holdings together with its subsidiaries (the Company) is a leading global life sciences company that is deeply integrated in guiding patient care, providing comprehensive clinical laboratory and end-to-end drug development services. The Company’s mission is to improve health and improve lives by delivering world-class diagnostic solutions, bringing innovative medicines to patients faster and using technology to provide better care. The Company serves a broad range of customers, including managed care organizations (MCOs), biopharmaceutical and medical device companies, governmental agencies, physicians and other health care providers (e.g., physician assistants and nurse practitioners, generally referred to herein as physicians), hospitals and health systems, employers, patients and consumers, contract research organizations (CROs), and independent clinical laboratories. The Company reports its business in two segments, LabCorp Diagnostics (LCD) and Covance Drug Development (CDD). For further financial information about these segments, see Note 15 Business Segment Information to the Condensed Consolidated Financial Statements. During the three months ended September 30, 2020, LCD and CDD contributed approximately 68% and 32% respectively, of revenues to the Company. During the nine months ended September 30, 2020, LCD and CDD contributed approximately 63% and 37%, respectively, of revenues to the Company. The condensed consolidated financial statements include the accounts of the Company and its majority-owned subsidiaries for which it exercises control. Long-term investments in affiliated companies in which the Company exercises significant influence, but which it does not control, are accounted for using the equity method. Investments in which the Company does not exercise significant influence (generally, when the Company has an investment of less than 20.0% and no representation on the investee's board of directors) are accounted for at fair value or at cost minus impairment adjusted for observable price changes in orderly transactions for an identical or similar investment of the same issuer for those investments that do not have readily determinable fair values. All significant inter-company transactions and accounts have been eliminated. The Company does not have any significant variable interest entities or special purpose entities whose financial results are not included in the condensed consolidated financial statements. The financial statements of the Company's operating foreign subsidiaries are measured using the local currency as the functional currency. Assets and liabilities are translated at exchange rates as of the balance sheet date. Revenues and expenses are translated at average monthly exchange rates prevailing during the period. Resulting translation adjustments are included in “Accumulated other comprehensive income.” The accompanying condensed consolidated financial statements of the Company are unaudited. In the opinion of management, all adjustments necessary for a fair statement of results of operations, cash flows, and financial position have been made. Except as otherwise disclosed, all such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for a full year. The year-end condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by generally accepted accounting principles. The condensed consolidated financial statements and notes are presented in accordance with the rules and regulations of the United States (U.S.) Securities and Exchange Commission (SEC) and do not contain certain information included in the Company’s 2019 Annual Report on Form 10-K (Annual Report). Therefore, these interim statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report.

BASIS OF FINANCIAL STATEMENT PRESENTATION

Laboratory Corporation of America® Holdings together with its subsidiaries (the Company) is a leading global life sciences company that is deeply integrated in guiding patient care, providing comprehensive clinical laboratory and end-to-end drug development services. The Company’s mission is to improve health and improve lives by delivering world-class diagnostic solutions, bringing innovative medicines to patients faster and using technology to provide better care. The Company serves a broad range of customers, including managed care organizations (MCOs), biopharmaceutical and medical device companies, governmental agencies, physicians and other health care providers (e.g., physician assistants and nurse practitioners, generally referred to herein as physicians), hospitals and health systems, employers, patients and consumers, contract research organizations (CROs), and independent clinical laboratories.

The Company reports its business in two segments, LabCorp Diagnostics (LCD) and Covance Drug Development (CDD). For further financial information about these segments, see Note 15 Business Segment Information to the Condensed Consolidated Financial Statements. During the three months ended September 30, 2020, LCD and CDD contributed approximately 68% and 32% respectively, of revenues to the Company. During the nine months ended September 30, 2020, LCD and CDD contributed approximately 63% and 37%, respectively, of revenues to the Company.

The condensed consolidated financial statements include the accounts of the Company and its majority-owned subsidiaries for which it exercises control. Long-term investments in affiliated companies in which the Company exercises significant influence, but which it does not control, are accounted for using the equity method. Investments in which the Company does not exercise significant influence (generally, when the Company has an investment of less than 20.0% and no representation on the investee's board of directors) are accounted for at fair value or at cost minus impairment adjusted for observable price changes in orderly transactions for an identical or similar investment of the same issuer for those investments that do not have readily determinable fair values. All significant inter-company transactions and accounts have been eliminated. The Company does not have any significant variable interest entities or special purpose entities whose financial results are not included in the condensed consolidated financial statements.

The financial statements of the Company's operating foreign subsidiaries are measured using the local currency as the functional currency. Assets and liabilities are translated at exchange rates as of the balance sheet date. Revenues and expenses are translated at average monthly exchange rates prevailing during the period. Resulting translation adjustments are included in “Accumulated other comprehensive income.”

The accompanying condensed consolidated financial statements of the Company are unaudited. In the opinion of management, all adjustments necessary for a fair statement of results of operations, cash flows, and financial position have been made. Except as otherwise disclosed, all such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for a full year. The year-end condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by generally accepted accounting principles.

The condensed consolidated financial statements and notes are presented in accordance with the rules and regulations of the United States (U.S.) Securities and Exchange Commission (SEC) and do not contain certain information included in the Company’s 2019 Annual Report on Form 10-K (Annual Report). Therefore, these interim statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report.

Recently Adopted Guidance

In June 2016, the FASB issued a new accounting standard intended to provide financial statement users with more decision-useful information about expected credit losses and other commitments to extend credit held by the reporting entity. The standard replaces the incurred loss impairment methodology in current generally accepted accounting principles (GAAP) with one that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The Company recorded an opening retained earnings adjustment of $7.0 with the adoption of this standard on January 1, 2020.

In August 2018, the FASB issued a new accounting standard to reduce, modify, and add to the disclosure requirements on fair value measurements. The Company adopted this standard effective January 1, 2020. The adoption of this standard did not have a material impact on the consolidated financial statements.

In August 2018, the FASB issued a new accounting standard to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred

to develop or obtain internal-use software. The Company adopted this standard effective January 1, 2020. The adoption of this standard did not have a material impact on the consolidated financial statements.

New Accounting Pronouncements

In August 2018, the FASB issued a new accounting standard to reduce, modify, and add to the disclosure requirements on defined benefit pension and other postretirement plans. The standard is effective on January 1, 2021, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the consolidated financial statements.

In December 2019, the FASB issued a new accounting standard to simplify accounting for income taxes and remove, modify, and add to the disclosure requirements of income taxes. The standard is effective January 1, 2021, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the consolidated financial statements.

In January 2020, the FASB issued a new accounting standard to clarify the interaction of the accounting for equity securities and investments accounted for under the equity method of accounting and the accounting for certain forward contracts and purchased options. The standard is effective January 1, 2021. The adoption of this standard is not expected to have a material impact on the consolidated financial statements.

In March 2020, the FASB issued a new accounting standard to provide optional expedients and exceptions if certain conditions are met for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The expedients and exceptions in the standard are effective between March 12, 2020, and December 31, 2022. The Company did not elect to apply any of the expedients or exceptions for the period ended September 30, 2020, and is currently evaluating the impact this new standard will have on the consolidated financial statements.

In August 2020, the FASB issued a new accounting standard to address issues identified as a result of the complexity associated with applying generally accepted accounting principles for convertible instruments and contracts in an entity's own equity. The standard is effective January 1, 2022, with early adoption permitted. The Company is evaluating the impact this new standard will have on the consolidated financial statements.

Novel Coronavirus (COVID-19) Financial Statement Impact

In March 2020, COVID-19 was declared a pandemic. COVID-19 has had and continues to have an extensive impact on the global health and economic environments. During the nine months ended September 30, 2020, the Company recorded goodwill and other asset impairment charges of $437.4, as a result of the negative financial impact of COVID-19 during the first quarter of 2020. See Note 6 Goodwill and Intangible Assets for a discussion of goodwill and intangible asset impairment and Note 2 Revenues for a discussion of credit losses and additional price concessions. The Company also impaired certain of the Company's investments by a total of $25.4 during the nine months ended September 30, 2020, due to the impact of COVID-19; $7.1 was included in Equity method earnings (loss), net during the three months ended March 31, 2020, and $13.1 and $5.2 were included in Other, net during the three months ended March 31, 2020, and June 30, 2020, respectively.

In April 2020, the Company received cash payments of approximately $55.9 from the Public Health and Social Services Emergency Fund for provider relief that was appropriated by Congress to the Department of Health and Human Services (HHS) in the Coronavirus Aid, Relief, and Economic Security Act (CARES Act Provider Relief Funds). Upon receiving and satisfying the terms and conditions associated with the distributed funds, the Company accounted for the transaction by applying the guidance in ASC 450-30 Gain Contingencies, and recorded these funds in Other, net non-operating income in the Consolidated Statement of Operations as of June 30, 2020. In August 2020, the Company received an additional $76.2 in CARES Act Provider Relief Funds. As the Company's Diagnostic business demonstrated recovery and demand for COVID-19 testing increased, the Company determined that the negative financial impact of COVID-19 which the CARES Act Provider Relief Funds were designed to address no longer applied to the Company. As a result, the Company derecognized the income associated with the $55.9 received during the second quarter as a change in estimate and did not recognize any income related to the cash payment of $76.2 received in the third quarter. The Company plans to return the CARES Act Provider Relief Funds to the government in the fourth quarter of 2020 and has recorded a liability of $132.1 in Accrued expenses and other as of September 30, 2020.

The extent to which the COVID-19 pandemic has and will impact the Company’s business and financial results depend on numerous evolving factors including, but not limited to: the magnitude and duration of the COVID-19 pandemic, the impact to worldwide macroeconomic conditions including interest rates, employment rates and health insurance coverage, the speed of the anticipated recovery, and governmental and business reactions to the pandemic. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to the Company and the unknown future impacts of COVID-19 as of September 30, 2020, and through the date of this