BASIS OF FINANCIAL STATEMENT PRESENTATION	3 Months Ended
Mar. 31, 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 companies, governmental agencies, physicians and other healthcare 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 16 Business Segment Information to the Condensed Consolidated Financial Statements. During the three months ended March 31, 2020, LCD and CDD contributed approximately 60% and 40%, 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 Company is currently evaluating the impact this new standard will have 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 Company is currently evaluating the impact this new standard will have 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 Company is currently evaluating the impact this new standard will have 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 March 31, 2020 and is currently evaluating the impact this new standard will have on the consolidated financial statements. Novel Coronavirus (COVID-19) Financial Statement Impact In March 2020, the novel strain of coronavirus, now known as COVID-19, was declared a pandemic. The COVID-19 pandemic has and continues to have an extensive impact on the global health and economic environments. By mid-March 2020, government restrictions, social distancing guidelines, and overall customer caution associated with the COVID-19 pandemic negatively affected LCD’s revenues and CDD's operations. For LCD, reduction in demand impacted testing volumes broadly but was more heavily weighted towards routine tests. This reduction in demand impacted testing volumes broadly but was more heavily weighted towards routine tests. The performance of CDD has also been negatively affected by the COVID-19 pandemic through numerous study site closures around the world as well as customer initiated delays for new patient recruitment for existing clinical trials and start-up of new clinical trials. As a result of the impact of the COVID-19 pandemic, during the three months ended March 31, 2020, the Company recorded goodwill and other asset impairment charges of $437.4: $426.4 within CDD and $11.0 within LCD. See Note 6 Goodwill and Intangible Assets for discussion of goodwill and intangible asset impairment and Note 2 Revenue for the discussion of credit losses and additional price concessions. The Company also wrote-off or wrote down certain of the Company's investments by $20.2 due to the impact of COVID-19, $7.1 included in Equity method earnings (loss), net and $13.1 included in Other, net. Use of Estimates The extent to which the COVID-19 pandemic impacts the Company’s business and financial results will depend on numerous evolving factors including, but not limited to: the magnitude and duration of the COVID-19 pandemic, the extent to which it will impact 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 March 31, 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, software, 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 companies, governmental agencies, physicians and other healthcare 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 16 Business Segment Information to the Condensed Consolidated Financial Statements. During the three months ended March 31, 2020, LCD and CDD contributed approximately 60% and 40%, 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

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 companies, governmental agencies, physicians and other healthcare 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 16 Business Segment Information to the Condensed Consolidated Financial Statements. During the three months ended March 31, 2020, LCD and CDD contributed approximately 60% and 40%, 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 Company is currently evaluating the impact this new standard will have 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 Company is currently evaluating the impact this new standard will have 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 Company is currently evaluating the impact this new standard will have 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 March 31, 2020 and is currently evaluating the impact this new standard will have on the consolidated financial statements.

Novel Coronavirus (COVID-19) Financial Statement Impact

In March 2020, the novel strain of coronavirus, now known as COVID-19, was declared a pandemic. The COVID-19 pandemic has and continues to have an extensive impact on the global health and economic environments. By mid-March 2020, government restrictions, social distancing guidelines, and overall customer caution associated with the COVID-19 pandemic negatively affected LCD’s revenues and CDD's operations. For LCD, reduction in demand impacted testing volumes broadly but was more heavily weighted towards routine tests. This reduction in demand impacted testing volumes broadly but was more heavily weighted towards routine tests. The performance of CDD has also been negatively affected by the COVID-19 pandemic through numerous study site closures around the world as well as customer initiated delays for new patient recruitment for existing clinical trials and start-up of new clinical trials. As a result of the impact of the COVID-19 pandemic, during the three months ended March 31, 2020, the Company recorded goodwill and other asset impairment charges of $437.4: $426.4 within CDD and $11.0 within LCD. See Note 6 Goodwill and Intangible Assets for discussion of goodwill and intangible asset impairment and Note 2 Revenue for the discussion of credit losses and additional price concessions. The Company also wrote-off or wrote down certain of the Company's investments by $20.2 due to the impact of COVID-19, $7.1 included in Equity method earnings (loss), net and $13.1 included in Other, net.

The extent to which the COVID-19 pandemic impacts the Company’s business and financial results will depend on numerous evolving factors including, but not limited to: the magnitude and duration of the COVID-19 pandemic, the extent to which it will impact 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 March 31, 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, software, 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 FINANCIAL STATEMENT PRESENTATION