BASIS OF FINANCIAL STATEMENT PRESENTATION	6 Months Ended
Jun. 30, 2019
Accounting Policies [Abstract]
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, medical device 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 believes that it generated more revenue from laboratory testing than any other company in the world in 2018. 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). During the three months ended June 30, 2019, LCD and CDD contributed approximately 61% and 39%, respectively, of revenues to the Company. During the six months ended June 30, 2019, LCD and CDD contributed approximately 61% and 39%, 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%) are accounted for at fair value or at cost minus impairment 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 2018 Annual Report on Form 10-K. 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 Leases In February 2016, the Financial Accounting Standards Board (FASB) issued a new accounting standard that sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. The Company has elected to utilize the short-term lease exemption and not record leases with initial terms of 12 months or less on the balance sheet. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases and direct financing leases. The Company adopted the standard on January 1, 2019, using the modified retrospective method. Comparative periods were not adjusted and are presented in accordance with lease guidance in effect for that period. The Company elected the package of practical expedients, which includes not reassessing whether existing contracts contain leases under the new definition of a lease, reassessing the classification of existing leases, and reassessing whether previously capitalized initial direct costs qualify for capitalization under the new standard. Leases with an initial term of 12 months or less are not recorded on the Condensed Consolidated Balance Sheets. Operating lease expense is recognized on a straight-line basis over the lease term. Operating lease assets and liabilities are recognized at the commencement date, based on the present value of the future minimum lease payments over the lease term. A certain number of these leases contain rent escalation clauses either fixed or adjusted periodically for inflation or market rates that are factored into the Company's determination of lease payments. The Company also has variable lease payments that do not depend on a rate or index, for items such as volume purchase commitments, which are recorded as variable cost when incurred. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date to discount payments to the present value. Some operating leases contain renewal options, some of which also include options to early terminate the leases. The exercise of these options is at the Company's discretion. The Company determined that all renewal options within leases for main laboratories, STAT laboratories, branches or combination sites were reasonably possible to be exercised and therefore are included in the accounting lease term. The standard had a material impact in the consolidated balance sheets, but no material impact in the consolidated income statements. The most significant impact was the recognition of right-of-use (ROU) assets and lease liabilities for operating leases, while the accounting for finance leases remained unchanged. New Accounting Pronouncements 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 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 update is effective on January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements. In August 2018, the FASB issued a new accounting standard to reduce, modify, and add to the disclosure requirements on fair value measurements. The standard is effective on January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements. 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 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 standard is effective on January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements. Reclassifications and Revisions The Company adopted Accounting Standard Update 2016-09 Compensation - Stock Compensation (Topic 718) during 2016 and incorrectly classified payments made to tax authorities for withheld shares from an employee’s equity award as cash flows from operating activities versus cash flows from financing activities. As a result, the Company has revised the consolidated statement of cash flows for these tax payments of $45.1 for the six months ended June 30, 2018, from operating activities to financing activities. The Company concluded that these errors were not material individually or in the aggregate to any of the periods impacted. In conjunction with the adoption of the new lease standard, the Company reclassified the capital lease asset balance of $44.4 at December 31, 2018, from Property, plant and equipment, net to Other assets.

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, medical device 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 believes that it generated more revenue from laboratory testing than any other company in the world in 2018.

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). During the three months ended June 30, 2019, LCD and CDD contributed approximately 61% and 39%, respectively, of revenues to the Company. During the six months ended June 30, 2019, LCD and CDD contributed approximately 61% and 39%, 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%) are accounted for at fair value or at cost minus impairment 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 2018 Annual Report on Form 10-K. Therefore, these interim statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report.

In February 2016, the Financial Accounting Standards Board (FASB) issued a new accounting standard that sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. The Company has elected to utilize the short-term lease exemption and not record leases with initial terms of 12 months or less on the balance sheet. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases and direct financing leases.

The Company adopted the standard on January 1, 2019, using the modified retrospective method. Comparative periods were not adjusted and are presented in accordance with lease guidance in effect for that period. The Company elected the package of practical expedients, which includes not reassessing whether existing contracts contain leases under the new definition of a lease, reassessing the classification of existing leases, and reassessing whether previously capitalized initial direct costs qualify for

Operating lease assets and liabilities are recognized at the commencement date, based on the present value of the future minimum lease payments over the lease term. A certain number of these leases contain rent escalation clauses either fixed or adjusted periodically for inflation or market rates that are factored into the Company's determination of lease payments. The Company also has variable lease payments that do not depend on a rate or index, for items such as volume purchase commitments, which are recorded as variable cost when incurred. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date to discount payments to the present value. Some operating leases contain renewal options, some of which also include options to early terminate the leases. The exercise of these options is at the Company's discretion. The Company determined that all renewal options within leases for main laboratories, STAT laboratories, branches or combination sites were reasonably possible to be exercised and therefore are included in the accounting lease term.

The standard had a material impact in the consolidated balance sheets, but no material impact in the consolidated income statements. The most significant impact was the recognition of right-of-use (ROU) assets and lease liabilities for operating leases, while the accounting for finance leases remained unchanged.

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 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 update is effective on January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements.

In August 2018, the FASB issued a new accounting standard to reduce, modify, and add to the disclosure requirements on fair value measurements. The standard is effective on January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements.

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 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 standard is effective on January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements.

The Company adopted Accounting Standard Update 2016-09 Compensation - Stock Compensation (Topic 718) during 2016 and incorrectly classified payments made to tax authorities for withheld shares from an employee’s equity award as cash flows from operating activities versus cash flows from financing activities. As a result, the Company has revised the consolidated statement of cash flows for these tax payments of $45.1 for the six months ended June 30, 2018, from operating activities to financing activities. The Company concluded that these errors were not material individually or in the aggregate to any of the periods impacted.