Laboratory Corporation of America (LH) 10-Q 30 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares shares in Millions	9 Months Ended
	Sep. 30, 2018	Oct. 26, 2018
Document Information [Line Items]
Entity Registrant Name	LABORATORY CORP OF AMERICA HOLDINGS
Entity Central Index Key	920,148
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		100.9
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 892.6	$ 316.6
Accounts Receivable, Net, Current	1,536.1	1,531
Unbilled Contracts Receivable	320.1	316.5
Supplies inventories	233	227.2
Prepaid expenses and other	292.5	308.8
Assets Held-for-sale, Not Part of Disposal Group, Current	0	33.7
Total current assets	3,274.3	2,733.8
Property, plant and equipment, net	1,734.3	1,706.6
Goodwill, net	7,362.7	7,400.9
Intangible Assets, Net (Excluding Goodwill)	3,990.9	4,166.1
Joint venture partnerships and equity method investments	57.9	58.4
Deferred Income Taxes and Other Assets, Current	1.9	1.9
Other assets, net	239.4	217.5
Assets Held-for-sale, Not Part of Disposal Group, Other	0	387.8
Total assets	16,661.4	16,673
Current liabilities:
Accounts payable	497.5	573.9
Deferred Revenue, Current	901.5	793.3
Deferred Tax Liabilities, Net, Current	289.4	380.8
Debt, Current	417.8	417.5
Disposal Group, Including Discontinued Operation, Liabilities, Current	0	20.2
Long-term debt, less current portion	2,106.2	2,185.7
Long-term Debt, Excluding Current Maturities	6,044.6	6,344.6
Commitments and contingent liabilities	343	376
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0	66.3
Noncontrolling interest	9,392.9	9,848.1
Shareholders' equity:
Common stock, 92.8 and 93.5 shares outstanding at March 31, 2013 and December 31, 2012, respectively	20.4	20.8
Additional paid-in capital	1,828.4	1,989.8
Retained earnings	11.9	12
Accumulated other comprehensive income	(6,921.9)	(6,196.1)
Total shareholders' equity	(1,106.3)	(1,060.1)
Total liabilities and shareholders' equity	(407.8)	(333.7)
Stockholders' Equity Attributable to Parent	7,248.1	6,804.1
Deferred income taxes and other tax liabilities	899.1	875.5
Liabilities and Equity	$ 16,661.4	$ 16,673

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parentheticals) - shares shares in Millions	Sep. 30, 2018	Dec. 31, 2017
Shareholders' Equity:
Common stock, shares outstanding (in shares)	101.4	101.9

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues	$ 2,831.3	$ 2,621.4	$ 8,545.9	$ 7,563.3
Cost of Revenue	2,041.4	1,837.2	6,141.9	5,288.6
Gross Profit	789.9	784.2	2,404	2,274.7
Selling, general and administrative expenses	381.8	381.3	1,174	1,081.9
Amortization of intangibles and other assets	54.7	54.6	175.5	153.6
Net restructuring and other special charges	10	21.6	36.5	64.6
Operating Income (Loss)	343.4	326.7	1,018	974.6
Other income (expenses):
Interest expense	(59.4)	(59.9)	(186)	(167.3)
Equity method income, net	3	3.2	8.5	10
Investment income	2.8	0.7	4.2	1.4
Other, net	209.8	(3.9)	209.1	(7.4)
Earnings before income taxes	499.6	266.8	1,053.8	811.3
Provision for income taxes	180.6	92.5	328.1	268.6
Net earnings	319	174.3	725.7	542.7
Less: Net earnings attributable to the noncontrolling interest	(0.2)	(2.8)	0.1	(3.4)
Net earnings attributable to Laboratory Corporation of America Holdings	$ 318.8	$ 171.5	$ 725.8	$ 539.3
Basic earnings per common share (in dollars per share)	$ 3.14	$ 1.68	$ 7.13	$ 5.27
Diluted earnings per common share (in dollars per share)	$ 3.10	$ 1.65	$ 7.04	$ 5.19
Previous Accounting Guidance [Member]
Gross profit, as reported		$ 882.8		$ 2,548.2
Net income (loss), including portion attributable to NCI, as reported		183.4		564.8
Net income (loss) attributable to Parent, as reported		180.6		561.4
Revenues		2,655.2		7,645.1
Cost of Revenue		1,772.4		5,096.9
Selling, general and administrative expenses		465.3		1,320
Other income (expenses):
Provision for income taxes		97.7		281.1
Less: Net earnings attributable to the noncontrolling interest		$ (2.8)		$ (3.4)
Basic earnings per common share (in dollars per share)		$ 1.77		$ 5.48
Diluted earnings per common share (in dollars per share)		$ 1.74		$ 5.40

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE EARNINGS (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net restructuring and other special charges	$ 10	$ 21.6	$ 36.5	$ 64.6
Provision for income taxes	180.6	92.5	328.1	268.6
Net earnings	319	174.3	725.7	542.7
Other Comprehensive Earnings, Net of Tax
Foreign currency translation adjustments	0.3	63	(82.2)	278.7
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	2.9	2.3	9.1	3.4
Other comprehensive earnings (loss) before tax	3.2	65.3	(73.1)	282.1
Tax effect of adjustments	(4)	(20.2)	(1)	(41)
Other comprehensive earnings (loss), net of tax	(0.8)	45.1	(74.1)	241.1
Comprehensive earnings	318.2	219.4	651.6	783.8
Less: Net earnings attributable to the noncontrolling interest	(0.2)	(2.8)	0.1	(3.4)
Comprehensive earnings attributable to Laboratory Corporation of America Holdings	$ 318	$ 216.6	$ 651.7	$ 780.4

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]
BALANCE at Dec. 31, 2016	$ 5,518.2	$ 12.1	$ 2,131.7	$ 4,969	$ (1,012.7)	$ (581.9)
Net earnings attributable to Laboratory Corporation of America Holdings	539.3			539.3
Other comprehensive earnings, net of tax	241.1					241.1
Issuance of common stock under employee stock plans	65.2	0.1	65.1
Surrender of restricted stock and performance share awards	(46.5)				(46.5)
Conversion of zero-coupon convertible debt	13.6		13.6		0
Stock compensation	85.8		85.8
Purchase of common stock	(298.1)	0.2	297.9
BALANCE at Sep. 30, 2017	6,118.6	12	1,998.3	5,508.3	(1,059.2)	(340.8)
BALANCE at Dec. 31, 2017	6,804.1	12	1,989.8	6,196.1	(1,060.1)	(333.7)
Net earnings attributable to Laboratory Corporation of America Holdings	725.8			725.8
Other comprehensive earnings, net of tax	(74.1)			0		(74.1)
Other Significant Noncash Transaction, Value of Consideration Given	67.4
Issuance of common stock under employee stock plans	46.2	0	67.4
Surrender of restricted stock and performance share awards					(46.2)
Conversion of zero-coupon convertible debt	0.3		0.3
Stock compensation	70.8		70.8
Purchase of common stock	(300)	0.1	299.9
BALANCE at Sep. 30, 2018	$ 7,248.1	$ 11.9	$ 1,828.4	$ 6,921.9	$ (1,106.3)	$ (407.8)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facilities	$ 449.2	$ 1,323.7
Noncontrolling interest distributions	(6.1)	(0.8)
Deferred payments on acquisitions	0	(1.6)
Repayments of Long-term Capital Lease Obligations	(6.8)	(6)
Payments Related to Tax Withholding for Share-based Compensation	(46.2)	(46.5)
Net proceeds from issuance of stock to employees	67.4	65.2
Payments for Repurchase of Common Stock	(300)	(298.1)
Repayments of Other Long-term Debt	295
Payments On Zero Coupon Subordinated Notes	(0.3)	(25.1)
Payments of Debt Issuance Costs	0	13.6
Repayments of Lines of Credit	(449.2)	(1,323.7)
Line of Credit Facility Payment		50
Net cash provided by (used for) financing activities	(587)	1,073.5
Repayments of Senior Debt	0	500
Proceeds from Issuance of Other Long-term Debt	0	750
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Disposal Group, Including Discontinued Operations		409.3
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents	0	0.2
Net earnings	725.7	542.7
Earnings before income taxes	1,053.8	811.3
Accreted interest on zero-coupon subordinated notes	0.1	0.3
Proceeds from Issuance of Long-term Debt	0	1,200
Adjustments to reconcile net earnings to net cash provided by operating activities:
Gain (Loss) on Disposition of Assets	(209.4)	0
Depreciation and amortization	414.4	388.2
Stock compensation	70.8	85.8
Loss on sale of assets	(1.9)	2.3
Cumulative earnings in excess of distributions from equity method investments	0.3	(0.4)
Asset Impairment Charges	5.3	23.5
Deferred income taxes	12.1	(0.1)
Change in assets and liabilities (net of effects of acquisitions):
Increase in accounts receivable (net)	(8.5)	(100.5)
Increase (Decrease) in Unbilled Receivables	(5.5)	(24.8)
Increase in inventories	(8.8)	(6.4)
Decrease in prepaid expenses and other	(40.1)	33.4
Decrease in accounts payable	(79.9)	109.1
Increase (Decrease) in Deferred Revenue	(94.4)	(1.1)
Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities	38.8	(118.9)
Net cash provided by operating activities	819	933.1
CASH FLOWS FROM INVESTING ACTIVITIES:
Increase (Decrease) in Assets Held-for-sale	654.5	0
Capital expenditures	(257.6)	(216.8)
Proceeds from sale of assets	50.1	1.2
Line of Credit Facility Payment		50
Payments to Acquire Intangible Assets	0	2.3
Investments in equity affiliates	(14.3)	(33.2)
Acquisition of businesses, net of cash acquired	(79.1)	(1,799.3)
Net cash used for investing activities	353.6	(2,050.4)
Effect of exchange rate changes on cash and cash equivalents	(9.6)	19.3
Net increase (decrease) in cash and cash equivalents	576	(24.5)
Cash and cash equivalents at beginning of period	316.6	433.6
Cash and cash equivalents at end of period	$ 892.6
Previous Accounting Guidance [Member]
Net cash provided by (used in) operating activities, as reported		895.3
CASH FLOWS FROM INVESTING ACTIVITIES:
Net increase (decrease) in cash and cash equivalents		$ (24.4)

BASIS OF FINANCIAL STATEMENT PR

BASIS OF FINANCIAL STATEMENT PRESENTATION	9 Months Ended
	Sep. 30, 2018
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, 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, food and nutritional companies and independent clinical laboratories. The Company believes that it generated more revenue from laboratory testing than any other company in the world in 2017. During the third quarter of 2018, the Company divested its forensic testing services business in the United Kingdom (U.K.) and its Food Solutions business. 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). During the three months ended September 30, 2018 , LCD and CDD contributed approximately 62% and 38% , respectively, of net revenues to the Company, and for the nine months ended September 30, 2018 , contributed approximately 62% and 38% , respectively. 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 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 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 2017 Annual Report on Form 10-K. Therefore, the 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 Revenue from Contracts with Customers In May 2014, the Financial Accounting Standards Board (FASB) issued the converged standard on revenue recognition with the objective of providing a single, comprehensive model for all contracts with customers to improve comparability in the financial statements of companies reporting using International Financial Reporting Standards (IFRS) and U.S. Generally Accepted Accounting Principles (GAAP). The standard contains principles that an entity must apply to determine the measurement of revenue and timing of when it is recognized. The underlying principle is that an entity must recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The standard was effective for the Company beginning January 1, 2018. The Company elected to adopt the standard using the full retrospective approach, which resulted in a recasting of revenue and the related financial statement items for 2016 and 2017. During transition to the new standard, the Company also elected several practical expedients, as provided by the standard. Contracts that began and ended within the same annual reporting period were not restated. Contracts that were completed by December 31, 2017, that had variable consideration were estimated using the transaction price at the date the contract was completed. The amount of the transaction price allocated to the remaining performance obligations will not be disclosed for prior reporting periods. Contracts that were modified prior to the earliest reporting period will be reflected in the earliest reporting period with an aggregate adjustment for prior modifications. As a result of the new standard, the Company has changed its accounting policies for revenue recognition. The significant changes under the new standard, and the quantitative impact of these changes, are detailed below. LCD The primary impact of the new standard to the LCD segment was classifying bad debt expense of $82.5 and $238.7 for the three and nine months ended September 30, 2017 , respectively, as a reduction in revenue rather than as a selling, general and administrative expense. CDD The primary impacts of the new standard to the CDD segment were as follows: Investigator fees : Prior to the new standard, reimbursements of investigator fees by clients were netted against the amounts paid to investigators in net revenues, on the basis that CDD was acting as the agent in arranging the investigator services. Under the new standard, revenue for investigator services and other reimbursable activities is recognized gross of fees paid to the investigators and other vendors, on the basis that a clinical study is considered a single, combined performance obligation for which CDD acts as a principal. Where CDD assumes the obligations by contract in studies involving patients, CDD is the principal because CDD may contract directly with third party clinical trial sites and investigators for investigator services and other reimbursable activities, which are combined with other CDD services in the management of a clinical study. Where CDD has assumed certain clinical trial sponsor obligations by contract in studies involving patients, CDD has primary responsibility for fulfilling its obligations associated with the full management of a clinical study, has inventory risk since it may be obligated to compensate investigators and other vendors for reimbursable activities regardless of payment by the customer, and has discretion within the framework agreed upon with the customer in setting the price of the study, including the budget for all pass-through costs, including investigator grants. The financial impact of this change on revenue for the three and nine months ended September 30, 2017, was an increase of $71.0 and $197.4 , respectively. Revenue and expenses from reimbursable out-of-pocket costs were previously recognized gross as separate line items from Net revenues and Net cost of revenue in the Consolidated Statement of Operations. Under the new standard, reimbursable out-of-pocket costs continue to be recognized gross, but are no longer presented separately (i.e., expenses are included in Cost of revenues and reimbursements are included in Revenues). In the statement of financial position, unbilled investigator fees and reimbursable out of pocket costs were reclassified from “Prepaid expenses and other” to “Unbilled services” and billed investigator grants and reimbursable out-of-pocket costs were reclassified from “Prepaid expenses and other” to “Accounts receivable, net.” Measure of progress : Prior to the new standard, service fee revenue in clinical studies was recognized on a proportional-performance basis, generally using output measures that are specific to the service provided (e.g., number of investigators enrolled, number of sites initiated, number of trial subjects enrolled and number of monitoring visits completed), while reimbursable out-of-pocket revenue was recognized when the associated expense was incurred. Changes in contract value from changes in scope were reflected once the customer agreed to the changes in scope and renegotiated pricing terms. Under the new standard, revenue in a clinical study (inclusive of budgeted reimbursable pass-through costs) is recognized using an input-based measure of progress based on costs incurred (including pass-through costs such as investigator services and reimbursable out-of-pocket expenses). If a customer’s approval of a work scope change creates an enforceable right to payment, the related revenue will be estimated and included in the measure of progress before a formal change order is executed, which results in recognition of revenue as services are provided. The financial impact of this change on revenue for the three and nine months ended September 30, 2017, was a decrease of $15.6 and $33.8 , respectively. Sales commissions : Prior to the new standard, sales commissions were recorded as an expense each quarter when incurred. Under the new standard, CDD amortizes sales commissions according to the expected service period to which the commissions relate on the basis that they are recoverable through the margin inherent in the contracts and recognizes the unamortized commissions as current and long-term assets. CDD applied the portfolio practical expedient in the new standard to determine the amortization period for assets recognized from sales commissions. Under the portfolio approach, CDD determined the weighted average contract term for groups of contracts with similar characteristics, and then amortized the capitalized sales commissions for that group over that term. CDD believes that any difference between the amortization patterns under the specific identification approach and the portfolio approach are not significant to CDD’s consolidated financial statements. The financial impact of this change on selling, general, and administrative expenses for the three and nine months ended September 30, 2017, was a decrease of $2.0 and $0.8 , respectively. The total quantitative impact of the new standard on retained earnings as of January 1, 2017, was an increase of $13.2 . New Accounting Pronouncements In February 2016, the 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. Leases with a term of 12 months or less will be accounted for based on guidance similar to current guidance for operating leases. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. The standard is effective on January 1, 2019, with early adoption permitted. The Company will adopt the standard using a modified retrospective transition approach and will not restate its comparative periods. The Company will implement a new module into the current leasing software solution which will facilitate compliance with the new standard. Given the size of the Company's lease portfolio, the adoption of this standard is expected to have a material impact on the Company's gross balance sheet with the recording of the right-to-use asset and a corresponding lease liability. 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 2016, the FASB issued a new accounting standard that makes eight targeted changes to how cash receipts and cash payments are presented and classified in the statement of cash flows. The Company adopted this standard on a retrospective basis effective January 1, 2018. As a result, the Company reclassified accreted interest paid upon conversion of its zero-coupon subordinated notes from a financing activity to an operating activity. In January 2017, the FASB issued a new accounting standard that changes the definition of a business to assist entities with evaluating when a set of transferred assets and activities is a business. The Company adopted this standard effective January 1, 2018. The adoption of this standard did not have a material impact on the consolidated financial statements as of September 30, 2018. In July 2017, the FASB issued a new accounting standard intended to reduce the complexity associated with the issuer's accounting for certain financial instruments with characteristics of liabilities and equity. Specifically, a down round feature would no longer cause a free-standing equity-linked financial instrument (or embedded conversion option) to be accounted for as a derivative liability at fair value with changes in fair value recognized in current earnings. This update is effective on January 1, 2019, with early adoption permitted and the option to use the retrospective or modified retrospective adoption method. The Company is currently evaluating the impact this new standard will have on the consolidated financial statements. In August 2017, the FASB issued a new accounting standard intended to more closely align hedge accounting with companies' risk management strategies, simplify the application of hedge accounting and increase transparency as to the scope and results of hedging programs. As a result, more hedging strategies are eligible for hedge accounting. The Company early adopted this standard effective January 1, 2018, and as allowed by the standard, elected to change the methodology for assessing hedge effectiveness of net investment hedges from a method based on changes in forward exchange rates to a method based on changes in spot exchange rates. The spot methodology under this standard allows the interest accrual components of hedge instruments to be reported directly in earnings while the changes in the fair value of hedge instruments attributable to changes in the spot rate are reported in the cumulative translation adjustment section of other comprehensive income. In August 2018, the FASB issued a new accounting standard to remove, 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 remove, 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 and $46.5 for the nine months ended September 30, 2017, 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. Adoption of the standards related to revenue recognition, pension accounting and cash receipts and payments as well as the revision for payments made to tax authorities for withheld shares from equity awards impacted previously reported results as follows: Condensed Consolidated Statement of Operations For the Three Months Ended September 30, 2017 As Previously Reported ASC 606 Revenue Adjustments Pension Adjustments As Adjusted Total revenues $ 2,655.2 $ (33.8 ) $ — $ 2,621.4 Total cost of revenue 1,772.4 64.6 0.2 1,837.2 Gross profit 882.8 (98.4 ) (0.2 ) 784.2 Selling, general and administrative expenses 465.3 (84.5 ) 0.5 381.3 Other operating and non-operating expenses, net 136.4 0.4 (0.7 ) 136.1 Provision for income taxes 97.7 (5.2 ) — 92.5 Net earnings 183.4 (9.1 ) — 174.3 Less: Net earnings attributable to noncontrolling interest (2.8 ) — — (2.8 ) Net earnings attributable to Laboratory Corporation of America Holdings $ 180.6 $ (9.1 ) $ — $ 171.5 Basic earnings per share $ 1.77 $ 1.68 Diluted earnings per share $ 1.74 $ 1.65 Condensed Consolidated Statement of Operations For the Nine Months Ended September 30, 2017 As previously reported ASC 606 Revenue Adjustments Pension Adjustments As Adjusted Total revenues $ 7,645.1 $ (81.8 ) $ — $ 7,563.3 Total cost of revenue 5,096.9 191.3 0.4 5,288.6 Gross profit 2,548.2 (273.1 ) (0.4 ) 2,274.7 Selling, general and administrative expenses 1,320.0 (239.4 ) 1.3 1,081.9 Other operating and non-operating expenses, net 382.3 0.9 (1.7 ) 381.5 Provision for income taxes 281.1 (12.5 ) — 268.6 Net earnings 564.8 (22.1 ) — 542.7 Less: Net earnings attributable to noncontrolling interest (3.4 ) — — (3.4 ) Net earnings attributable to Laboratory Corporation of America Holdings $ 561.4 $ (22.1 ) $ — $ 539.3 Basic earnings per share $ 5.48 $ 5.27 Diluted earnings per share $ 5.40 $ 5.19 Condensed Consolidated Statement of Cash Flows For the Nine Months Ended September 30, 2017 As Previously Reported Tax Payments for Equity Awards Revision ASC 606 Revenue Adjustments Zero-Coupon Notes Adjustments As Adjusted Net cash provided by operating activities $ 895.3 $ 46.5 $ — $ (8.7 ) $ 933.1 Net cash used for investing activities (2,050.4 ) — — — (2,050.4 ) Net cash provided by financing activities 1,111.3 (46.5 ) — 8.7 1,073.5 Effect of exchange rate changes on cash and cash equivalents 19.4 — (0.1 ) — 19.3 Net decrease in cash and cash equivalents $ (24.4 ) $ (24.5 ) The below adjustments have been made to the December 31, 2017, balance sheet and are all the result of the implementation of ASC 606. The adjustments include a cumulative catch-up adjustment, reclassification of unbilled services, and the capitalization of contract acquisition costs. Condensed Consolidated Balance Sheets December 31, 2017 As Previously Reported ASC 606 Revenue Adjustments As Adjusted Current assets $ 2,682.6 $ 51.2 $ 2,733.8 Long-term assets 13,885.4 53.8 13,939.2 Total assets $ 16,568.0 $ 105.0 $ 16,673.0 Current liabilities $ 2,046.1 $ 139.6 $ 2,185.7 Long-term liabilities 7,671.1 (8.7 ) 7,662.4 Noncontrolling interest 20.8 — 20.8 Shareholders' equity 6,830.0 (25.9 ) 6,804.1 Total liabilities and shareholders' equity $ 16,568.0 $ 105.0 $ 16,673.0

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share is computed by dividing net earnings attributable to Laboratory Corporation of America Holdings by the weighted average number of common shares outstanding. Diluted earnings per share is computed by dividing net earnings including the impact of dilutive adjustments by the weighted average number of common shares outstanding plus potentially dilutive shares, as if they had been issued at the earlier of the date of issuance or the beginning of the period presented. Potentially dilutive common shares result primarily from the Company’s outstanding stock options, restricted stock awards, restricted stock units, performance share awards, and shares issuable upon conversion of zero-coupon subordinated notes. The following represents a reconciliation of basic earnings per share to diluted earnings per share: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Earnings Shares Per Share Amount Earnings Shares Per Share Amount Earnings Shares Per Share Amount Earnings Shares Per Share Amount Basic earnings per share: Net earnings $ 318.8 101.6 $ 3.14 $ 171.5 102.2 $ 1.68 $ 725.8 101.8 $ 7.13 $ 539.3 102.4 $ 5.27 Dilutive effect of employee stock options and awards — 1.0 — 1.4 — 1.2 — 1.4 Effect of convertible debt — 0.1 — 0.1 — 0.1 — 0.1 Diluted earnings per share: Net earnings including impact of dilutive adjustments $ 318.8 102.7 $ 3.10 $ 171.5 103.7 $ 1.65 $ 725.8 $ 103.1 $ 7.04 $ 539.3 $ 103.9 $ 5.19 The following table summarizes the potential common shares not included in the computation of diluted earnings per share because their impact would have been antidilutive: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Stock options 0.1 0.1 0.1 0.1

RESTRUCTURING AND OTHER SPECIAL

RESTRUCTURING AND OTHER SPECIAL CHARGES	9 Months Ended
	Sep. 30, 2018
Restructuring and Related Activities [Abstract]
Restructuring and Related Activities Disclosure [Text Block]	RESTRUCTURING AND OTHER SPECIAL CHARGES During the nine months ended September 30, 2018 , the Company recorded net restructuring and other special charges of $36.5 : $13.2 within LCD and $23.3 within CDD. The charges were comprised of $30.0 related to severance and other personnel costs and $8.8 in costs associated with facility closures and general integration initiatives. The charges were offset by the reversal of previously established reserves of $1.2 and $1.1 in unused facility reserves and unused severance reserves, respectively. The Company also recorded $5.3 in impairment to land held for sale which is included in amortization expense. The Company incurred integration and other costs of $43.1 primarily relating to the Chiltern acquisition and the sale of the Food Solutions business. On July 16, 2018, the Company reported that it had detected suspicious activity on its information technology network and was taking steps to respond to and contain the activity. The activity was subsequently determined to be a new variant of ransomware affecting certain LCD information technology systems. As a direct result of the ransomware attack experienced during July, the Company incurred $12.6 in consulting fees and employee overtime during the recovery period following the attack. The Company also recorded $4.3 in consulting expenses relating to the Chiltern integration and management integration costs along with a special one-time bonus of $31.1 to its non-bonus eligible employees in recognition of the benefits the Company is receiving from the passage of the Tax Cuts and Jobs Act of 2017 (TCJA). In addition, the Company incurred $7.3 of non-capitalized costs associated with the implementation of a major system as part of its LaunchPad business process improvement initiative. During the nine months ended September 30, 2017 , the Company recorded net restructuring and other special charges of $64.6 : $14.0 within LCD and $50.6 within CDD. The charges were comprised of $27.2 related to severance and other personnel costs along with $18.0 in costs associated with facility closures and general integration initiatives. The Company reversed previously established reserves of $1.4 in unused severance reserves and $0.1 in unused facility reserves. Also included in the net restructuring and other special charges is an impairment loss of $20.9 related to the termination of a software development project within the CDD segment and the forgiveness of certain indebtedness for LCD customers in areas heavily impacted by hurricanes during the third quarter. The Company incurred legal and other costs of $29.8 relating to the recently completed acquisitions. The Company also recorded $8.0 in consulting expenses relating to fees incurred as part of its integration and compensation analysis, along with $0.9 in short-term equity retention arrangements relating to the Covance Inc. acquisition. In addition, the Company incurred $8.2 of non-capitalized costs associated with the implementation of a major system as part of LaunchPad (all recorded in selling, general and administrative expenses). The following represents the Company’s restructuring reserve activities for the period indicated: LCD CDD Severance and Other Employee Costs Lease and Other Facility Costs Severance and Other Employee Costs Lease and Other Facility Costs Total Balance as of December 31, 2017 $ 1.7 $ 10.1 $ 8.3 $ 34.6 $ 54.7 Restructuring charges 10.7 3.0 19.3 5.8 38.8 Reduction of prior restructuring accruals — (0.5 ) (1.2 ) (0.6 ) (2.3 ) Cash payments and other adjustments (11.1 ) (5.3 ) (16.3 ) (10.4 ) (43.1 ) Balance as of September 30, 2018 $ 1.3 $ 7.3 $ 10.1 $ 29.4 $ 48.1 Current $ 22.6 Non-current 25.5 $ 48.1

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	GOODWILL AND INTANGIBLE ASSETS The changes in the carrying amount of goodwill for the nine-month period ended September 30, 2018 , and for the year ended December 31, 2017 , are as follows: LCD CDD Total September 30, December 31, 2017 September 30, December 31, 2017 September 30, December 31, 2017 Balance as of January 1 $ 3,673.9 $ 3,644.8 $ 3,727.0 $ 2,779.6 $ 7,400.9 $ 6,424.4 Goodwill acquired during the period 3.9 198.5 45.6 811.3 49.5 1,009.8 Reclassification of goodwill as held for sale — (170.5 ) — — — (170.5 ) Dispositions (24.1 ) — — — (24.1 ) — Adjustments to goodwill (4.2 ) 1.1 (59.4 ) 136.1 (63.6 ) 137.2 Balance at end of period $ 3,649.5 $ 3,673.9 $ 3,713.2 $ 3,727.0 $ 7,362.7 $ 7,400.9 The components of identifiable intangible assets are as follows: September 30, 2018 December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Customer relationships $ 4,115.7 $ (1,106.5 ) $ 3,009.2 $ 4,118.1 $ (992.8 ) $ 3,125.3 Patents, licenses and technology 454.6 (207.8 ) 246.8 457.9 (188.6 ) 269.3 Non-compete agreements 75.8 (53.0 ) 22.8 75.8 (48.3 ) 27.5 Trade names 405.0 (183.3 ) 221.7 407.9 (167.9 ) 240.0 Land use right 10.8 (3.7 ) 7.1 10.8 (2.5 ) 8.3 Canadian licenses 483.3 — 483.3 495.7 — 495.7 $ 5,545.2 $ (1,554.3 ) $ 3,990.9 $ 5,566.2 $ (1,400.1 ) $ 4,166.1 Amortization of intangible assets for the three-month periods ended September 30, 2018 , and 2017 , was $54.7 and $54.6 , respectively, and $175.5 and $153.6 for the nine-month periods ended September 30, 2018 , and 2017 . Amortization expense for the net carrying amount of intangible assets is estimated to be $51.3 for the remainder of fiscal 2018 , $ 222.5 in fiscal 2019 , $214.4 in fiscal 2020 , $208.1 in fiscal 2021 , $202.5 in fiscal 2022 and $2,522.8 thereafter.

DEBT

DEBT	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	DEBT Short-term borrowings and the current portion of long-term debt at September 30, 2018 , and December 31, 2017 , consisted of the following: September 30, December 31, 2017 Zero-coupon convertible subordinated notes $ 8.6 $ 8.8 2.50% senior notes due 2018 400.0 400.0 Debt issuance costs (0.6 ) (1.4 ) Current portion of capital leases 8.0 8.3 Current portion of note payable 1.8 1.8 Total short-term borrowings and current portion of long-term debt $ 417.8 $ 417.5 Long-term debt at September 30, 2018 , and December 31, 2017 , consisted of the following: September 30, December 31, 2017 2.625% senior notes due 2020 $ 500.0 $ 500.0 4.625% senior notes due 2020 599.5 604.1 3.20% senior notes due 2022 500.0 500.0 3.75% senior notes due 2022 500.0 500.0 4.00% senior notes due 2023 300.0 300.0 3.25% senior notes due 2024 600.0 600.0 3.60% senior notes due 2025 1,000.0 1,000.0 3.60% senior notes due 2027 600.0 600.0 4.70% senior notes due 2045 900.0 900.0 2014 Term loan — 72.0 2017 Term loan 527.0 750.0 Debt issuance costs (42.0 ) (48.2 ) Capital leases 52.6 57.8 Note payable 7.5 8.9 Total long-term debt $ 6,044.6 $ 6,344.6 Senior Notes On August 22, 2017, the Company issued new senior notes representing $ 1,200.0 in debt securities and consisting of a $ 600.0 aggregate principal amount of 3.25% senior notes due 2024 and a $ 600.0 aggregate principal amount of 3.60% senior notes due 2027. Interest on these notes is payable semi-annually on March 1 and September 1 of each year, commencing on March 1, 2018. Net proceeds from the offering of these notes were $ 1,190.1 after deducting underwriting discounts and other expenses of the offering. Net proceeds were used to pay off the 2.20% senior notes due August 23, 2017, as well as a portion of the cash consideration and the fees and expenses in connection with the Chiltern acquisition. During the third quarter of 2013, the Company entered into two fixed-to-variable interest rate swap agreements for its 4.625% senior notes due 2020 with an aggregate notional amount of $600.0 and variable interest rates based on one-month LIBOR plus 2.298% to hedge against changes in the fair value of a portion of the Company's long-term debt. These derivative financial instruments are accounted for as fair value hedges of the senior notes due 2020. These interest rate swaps are included in other long-term assets or other long-term liabilities, as applicable, and added to or subtracted from the value of the senior notes, with an aggregate fair value of $ 0.5 (liability) at September 30, 2018 , and $4.1 (asset) at December 31, 2017 . During the first quarter of 2018, the Company entered into six USD to Swiss Franc cross-currency swap agreements with an aggregate notional value of $600.0 and which are accounted for as a hedge against its net investment in a Swiss subsidiary. Of the notional value, $300.0 matures in 2022 and $300.0 matures in 2025. The cross currency swaps maturing in 2022 and 2025 are included in other long-term assets with an aggregate fair value of $6.6 and $1.5 , respectively, as of September 30, 2018 . Changes in the fair value of the cross-currency swaps are charged or credited through accumulated other comprehensive income in the Consolidated Balance Sheet until the hedged item is recognized in earnings. Zero-Coupon Subordinated Notes On September 11, 2018, the Company announced that for the period from September 11, 2018, to March 8, 2019, the zero-coupon subordinated notes will accrue contingent cash interest at a rate of no less than 0.125% of the average market price of a zero-coupon subordinated note for the five trading days ended September 7, 2018, in addition to the continued accrual of the original issue discount. During the nine months ended September 30, 2018 , the Company settled notices to convert $0.3 aggregate principal amount of its zero-coupon subordinated notes with a conversion value of $0.7 . The total cash used for these settlements was $0.3 and the Company also issued 0.0 shares of common stock. As a result of these conversions, the Company also reversed deferred tax liabilities of $0.2 . On October 1, 2018, the Company announced that its zero-coupon subordinated notes may be converted into cash and common stock at the conversion rate of 13.4108 per $1,000.0 principal amount at maturity of the notes, subject to the terms of the zero-coupon subordinated notes and the Indenture, dated as of October 24, 2006 , between the Company and The Bank of New York Mellon, as trustee and the conversion agent. In order to exercise the option to convert all or a portion of the zero-coupon subordinated notes, holders are required to validly surrender their zero-coupon subordinated notes at any time during the calendar quarter beginning October 1, 2018, through the close of business on the last business day of the calendar quarter, which is 5:00 p.m., New York City time, on Monday, December 31, 2018. If notices of conversion are received, the Company plans to settle the cash portion of the conversion obligation with cash on hand and/or borrowings under the revolving credit facility. Credit Facilities On September 15, 2017, the Company entered into a new $750.0 term loan in addition to its existing $1,000.0 term loan entered into in December 2014. The 2017 term loan facility will mature on September 15, 2022. The 2014 term loan balance at September 30, 2018 , was $0.0 and at December 31, 2017 , was $72.0 . The 2017 term loan balance at September 30, 2018 , was $527.0 and at December 31, 2017 , was $750.0 . The 2014 term loan credit facility accrued interest at a per annum rate equal to, at the Company’s election, either a LIBOR rate plus a margin ranging from 1.125% to 2.00% , or a base rate determined according to a prime rate or federal funds rate plus a margin ranging from 0.125% to 1.00% . The 2017 term loan credit facility accrues interest at a per annum rate equal to, at the Company’s election, either a LIBOR rate plus a margin ranging from 0.875% to 1.50% , or a base rate determined according to a prime rate or federal funds rate plus a margin ranging from 0.0% to 0.50% . The Company paid off the 2014 term loan during the second quarter of 2018. As of September 30, 2018 , the effective interest rate on the 2017 term loan was 3.37% . The Company entered into a senior revolving credit facility on December 21, 2011, which was amended and restated on December 19, 2014, further amended on July 13, 2016, and further amended and restated on September 15, 2017. The senior revolving credit facility consists of a five-year revolving facility in the principal amount of up to $1,000.0 , with the option of increasing the facility by up to an additional $350.0 , subject to the agreement of one or more new or existing lenders to provide such additional amounts and certain other customary conditions. The revolving credit facility also provides for a subfacility of up to $100.0 for swing line borrowings and a subfacility of up to $150.0 for issuances of letters of credit. The revolving credit facility is permitted to be used for general corporate purposes, including working capital, capital expenditures, funding of share repurchases and certain other payments, and acquisitions and other investments. The outstanding balance on the Company's revolving credit facility was $0.0 at September 30, 2018 , and December 31, 2017 . Advances under the revolving credit facility will accrue interest at a per annum rate equal to, at the Company’s election, either a LIBOR rate plus a margin ranging from 0.775% to 1.25% , or a base rate determined according to a prime rate or federal funds rate plus a margin ranging from 0.00% to 0.25% . Fees are payable on outstanding letters of credit under the revolving credit facility at a per annum rate equal to the applicable margin for LIBOR loans, and the Company is required to pay a facility fee on the aggregate commitments under the revolving credit facility, at a per annum rate ranging from 0.10% to 0.25% . The interest margin applicable to the credit facilities, and the facility fee and letter of credit fees payable under the revolving credit facility, are based on the Company’s senior credit ratings as determined by Standard & Poor’s and Moody’s. Under the term loan facilities and the revolving credit facility, the Company is subject to negative covenants limiting subsidiary indebtedness and certain other covenants typical for investment grade-rated borrowers, and the Company is required to maintain certain leverage ratios. The Company was in compliance with all covenants in the term loan facilities and the revolving credit facility at September 30, 2018 . As of September 30, 2018 , the ratio of total debt to consolidated proforma trailing 12 month EBITDA was 3.1 to 1.0.

PREFERRED STOCK AND COMMON SHAR

PREFERRED STOCK AND COMMON SHAREHOLDERS' EQUITY	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Changes in common shares issued and held in treasury	The changes in common shares issued and held in treasury are summarized below: Issued Held in Treasury Outstanding Common shares at December 31, 2017 125.1 (23.2 ) 101.9 Common stock issued under employee stock plans 1.5 — 1.5 Surrender of restricted stock and performance share awards — (0.3 ) (0.3 ) Retirement of common stock (1.7 ) — (1.7 ) Common shares at September 30, 2018 124.9 (23.5 ) 101.4
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The components of accumulated other comprehensive earnings are as follows: Foreign Currency Translation Adjustments Net Benefit Plan Adjustments Accumulated Other Comprehensive Earnings (Loss) Balance at December 31, 2017 $ (240.7 ) $ (93.0 ) $ (333.7 ) Other comprehensive earnings (loss) before reclassifications (82.2 ) 9.1 (73.1 ) Tax effect of adjustments 2.5 (3.5 ) (1.0 ) Balance at September 30, 2018 $ (320.4 ) $ (87.4 ) $ (407.8 )
Accumulated Other Comprehensive Income (Loss) [Line Items]
Preferred Stock and Common Shareholders' Equity	PREFERRED STOCK AND COMMON SHAREHOLDERS’ EQUITY The Company is authorized to issue up to 265.0 shares of common stock, par value $0.10 per share. The Company’s treasury shares are recorded at aggregate cost. The Company is authorized to issue up to 30.0 shares of preferred stock, par value $0.10 per share. There were no preferred shares outstanding as of September 30, 2018 , and December 31, 2017. The changes in common shares issued and held in treasury are summarized below: Issued Held in Treasury Outstanding Common shares at December 31, 2017 125.1 (23.2 ) 101.9 Common stock issued under employee stock plans 1.5 — 1.5 Surrender of restricted stock and performance share awards — (0.3 ) (0.3 ) Retirement of common stock (1.7 ) — (1.7 ) Common shares at September 30, 2018 124.9 (23.5 ) 101.4 Share Repurchase Program At the end of 2017, the Company had outstanding authorization from the board of directors to purchase up to $401.4 of Company common stock. During the nine months ended September 30, 2018 , the Company purchased 1.7 shares of its common stock at a total cost of $300.0 . On April 24, 2018, the board authorized an increase in the Company’s share repurchase program to a total of $1,000.0 . As of September 30, 2018 , the Company had outstanding authorization from the board of directors to purchase up to $843.5 of Company common stock. The repurchase authorization has no expiration. Accumulated Other Comprehensive Earnings The components of accumulated other comprehensive earnings are as follows: Foreign Currency Translation Adjustments Net Benefit Plan Adjustments Accumulated Other Comprehensive Earnings (Loss) Balance at December 31, 2017 $ (240.7 ) $ (93.0 ) $ (333.7 ) Other comprehensive earnings (loss) before reclassifications (82.2 ) 9.1 (73.1 ) Tax effect of adjustments 2.5 (3.5 ) (1.0 ) Balance at September 30, 2018 $ (320.4 ) $ (87.4 ) $ (407.8 )

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The Company does not recognize a tax benefit unless the Company concludes that it is more likely than not that the benefit will be sustained on audit by the taxing authority based solely on the technical merits of the associated tax position. If the recognition threshold is met, the Company recognizes a tax benefit measured at the largest amount of the tax benefit that the Company believes is greater than 50% likely to be realized. The gross unrecognized income tax benefits were $18.8 and $19.5 at September 30, 2018 , and December 31, 2017 , respectively. It is anticipated that the amount of the unrecognized income tax benefits will change within the next 12 months; however, these changes are not expected to have a significant impact on the results of operations, cash flows or the financial position of the Company. As of September 30, 2018 , and December 31, 2017 , $18.8 and $19.5 , respectively, are the approximate amounts of gross unrecognized income tax benefits that, if recognized, would favorably affect the effective income tax rate in future periods. The Company recognizes interest and penalties related to unrecognized income tax benefits in income tax expense. Accrued interest and penalties related to uncertain tax positions totaled $8.6 and $7.9 as of September 30, 2018 , and December 31, 2017 , respectively. The Company has substantially concluded all U.S. federal income tax matters for years through 2014. Substantially all material state and local, and foreign income tax matters have been concluded through 2013 and 2014, respectively. During the quarter, the IRS concluded its examination of Covance's 2013 federal income tax return. The IRS has not initiated a new examination of any of the Company's federal income tax returns. The Canada Revenue Agency is currently examining the Company's Canadian subsidiaries' 2013, 2014, and 2015 tax returns. The Company has various state and foreign income tax examinations ongoing throughout the year. The Company believes adequate provisions have been recorded related to all open tax years. On December 22, 2017, the SEC issued Staff Accounting Bulletin No. 118 (SAB 118), which provides companies with additional guidance on how to account for the TCJA in its financial statements, allowing companies to use a measurement period. At September 30, 2018, the Company had not completed the accounting for the tax effects of enactment of the TCJA; however, a reasonable estimate on the re-measurement of the Company's existing deferred tax balances, the deferred tax revaluation for unremitted foreign earnings, and the one-time repatriation tax has been made. For these items, in accordance with SAB 118, a provisional net benefit of $519.0 was recognized in the fourth quarter of 2017. During the nine months ended September 30, 2018 , the Company continued its review and recorded net additional provisional expense of $28.1 in the quarter, for a year to date total of $44.1 . The TCJA includes provisions relating to global intangible low-taxed income (GILTI). Relevant to the current consolidated financial statements is the Company's selection of an accounting policy with respect to the new GILTI tax rules, and whether to account for GILTI as a periodic charge in the period it arises or to record deferred taxes associated with the basis in the Company's foreign subsidiaries. Due to the intricacy of this topic, the Company is still in the process of investigating the implications of accounting for the GILTI tax and intends to make an accounting policy decision once additional guidance is available for assessment. During the nine months ended September 30, 2018, the Company recorded its estimated GILTI tax as a periodic charge.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES The Company is involved from time to time in various claims and legal actions, including arbitrations, class actions, and other litigation (including those described in more detail below), arising in the ordinary course of business. Some of these actions involve claims that are substantial in amount. These matters include, but are not limited to, intellectual property disputes; commercial and contract disputes; professional liability; employee-related matters; and inquiries, including subpoenas and other civil investigative demands, from governmental agencies, Medicare or Medicaid payers and MCOs reviewing billing practices or requesting comment on allegations of billing irregularities that are brought to their attention through billing audits or third parties. The Company receives civil investigative demands or other inquiries from various governmental bodies in the ordinary course of its business. Such inquiries can relate to the Company or other parties, including physicians and other healthcare providers (e.g., physician assistants and nurse practitioners, generally referred to herein as physicians). The Company works cooperatively to respond to appropriate requests for information. The Company also is named from time to time in suits brought under the qui tam provisions of the False Claims Act and comparable state laws. These suits typically allege that the Company has made false statements and/or certifications in connection with claims for payment from U.S. federal or state healthcare programs. The suits may remain under seal (hence, unknown to the Company) for some time while the government decides whether to intervene on behalf of the qui tam plaintiff. Such claims are an inevitable part of doing business in the healthcare field today. The Company believes that it is in compliance in all material respects with all statutes, regulations and other requirements applicable to its commercial laboratory operations and drug development support services. The healthcare diagnostics and drug development industries are, however, subject to extensive regulation, and the courts have not interpreted many of the applicable statutes and regulations. Therefore, the applicable statutes and regulations could be interpreted or applied by a prosecutorial, regulatory or judicial authority in a manner that would adversely affect the Company. Potential sanctions for violation of these statutes and regulations include significant civil and criminal penalties, fines, the loss of various licenses, certificates and authorizations, additional liabilities from third-party claims, and/or exclusion from participation in government programs. Many of the current claims and legal actions against the Company are in preliminary stages, and many of these cases seek an indeterminate amount of damages. The Company records an aggregate legal reserve, which is determined using calculations based on historical loss rates and assessment of trends experienced in settlements and defense costs. In accordance with FASB Accounting Standards Codification Topic 450 “Contingencies,” the Company establishes reserves for judicial, regulatory, and arbitration matters outside the aggregate legal reserve if and when those matters present loss contingencies that are both probable and estimable and would exceed the aggregate legal reserve. When loss contingencies are not both probable and estimable, the Company does not establish separate reserves. The Company is unable to estimate a range of reasonably probable loss for the proceedings described in more detail below in which damages either have not been specified or, in the Company's judgment, are unsupported and/or exaggerated and (i) the proceedings are in early stages; (ii) there is uncertainty as to the outcome of pending appeals or motions; (iii) there are significant factual issues to be resolved; and/or (iv) there are novel legal issues to be presented. For these proceedings, however, the Company does not believe, based on currently available information, that the outcomes will have a material adverse effect on the Company's financial condition, though the outcomes could be material to the Company's operating results for any particular period, depending, in part, upon the operating results for such period. As previously reported, the Company responded to an October 2007 subpoena from the U.S. Department of Health & Human Services Office of Inspector General's regional office in New York. On August 17, 2011, the U.S. District Court for the Southern District of New York unsealed a False Claims Act lawsuit, United States of America ex rel. NPT Associates v. Laboratory Corporation of America Holdings , which alleges that the Company offered UnitedHealthcare kickbacks in the form of discounts in return for Medicare business. The Plaintiff's Third Amended Complaint further alleges that the Company's billing practices violated the False Claims Acts of 14 states and the District of Columbia. The lawsuit seeks actual and treble damages and civil penalties for each alleged false claim, as well as recovery of costs, attorney's fees, and legal expenses. Neither the U.S. government nor any state government has intervened in the lawsuit. The Company's Motion to Dismiss was granted in October 2014 and Plaintiff was granted the right to replead. On January 11, 2016, Plaintiff filed a motion requesting leave to file an amended complaint under seal and to vacate the briefing schedule for the Company's Motion to Dismiss, while the government reviews the amended complaint. The Court granted the motion and vacated the briefing dates. Plaintiff then filed the Amended Complaint under seal. The Company will vigorously defend the lawsuit. In addition, the Company has received various other subpoenas since 2007 related to Medicaid billing. In October 2009, the Company received a subpoena from the State of Michigan Department of Attorney General seeking documents related to its billing to Michigan Medicaid. The Company cooperated with this request. In October 2013, the Company received a Civil Investigative Demand from the State of Texas Office of the Attorney General requesting documents related to its billing to Texas Medicaid. The Company cooperated with this request. On October 5, 2018, the Company received a second Civil Investigative Demand from the State of Texas Office of the Attorney General requesting documents related to its billing to Texas Medicaid. The Company is cooperating with this request. On May 2, 2013, the Company was served with a False Claims Act lawsuit, State of Georgia ex rel. Hunter Laboratories, LLC and Chris Riedel v. Quest Diagnostics Incorporated, et al. , filed in the State Court of Fulton County, Georgia. The lawsuit, filed by a competitor laboratory, alleges that the Company overcharged Georgia's Medicaid program. The State of Georgia filed a Notice of Declination on August 13, 2012, before the Company was served with the Complaint. The case was removed to the U.S. District Court for the Northern District of Georgia. The lawsuit seeks actual and treble damages and civil penalties for each alleged false claim, as well as recovery of costs, attorney's fees, and legal expenses. On March 14, 2014, the Company's Motion to Dismiss was granted. The Plaintiffs repled their complaint, and the Company filed a Motion to Dismiss the First Amended Complaint. In May 2015, the Court dismissed the Plaintiffs' anti-kickback claim and remanded the remaining state law claims to the State Court of Fulton County. In July 2015, the Company filed a Motion to Dismiss these remaining claims. The Plaintiffs filed an opposition to the Company's Motion to Dismiss in August 2015. Also, the State of Georgia filed a brief as amicus curiae. The parties have reached a settlement in principle. On August 24, 2012, the Company was served with a putative class action lawsuit, Sandusky Wellness Center, LLC, et al. v. MEDTOX Scientific, Inc., et al. , filed in the U.S. District Court for the District of Minnesota. The lawsuit alleges that on or about February 21, 2012, the defendants violated the U.S. Telephone Consumer Protection Act (TCPA) by sending unsolicited facsimiles to Plaintiff and more than 39 other recipients without the recipients' prior express invitation or permission. The lawsuit seeks the greater of actual damages or the sum of $0.0005 for each violation, subject to trebling under the TCPA, and injunctive relief. In September of 2014, Plaintiff’s Motion for Class Certification was denied. In January of 2015, the Company's Motion for Summary Judgment on the remaining individual claim was granted. Plaintiff filed a notice of appeal. On May 3, 2016, the U.S. Court of Appeals for the Eighth Circuit issued its decision and order reversing the District Court's denial of class certification. The Eighth Circuit remanded the matter for further proceedings. On December 7, 2016, the District Court granted the Plaintiff’s renewed Motion for Class Certification. The parties have reached a settlement in principle, which will require Court approval. On August 31, 2015, the Company was served with a putative class action lawsuit, Patty Davis v. Laboratory Corporation of America, et al., filed in the Circuit Court of the Thirteenth Judicial Circuit for Hillsborough County, Florida. The Complaint alleges that the Company violated the Florida Consumer Collection Practices Act by billing patients who were collecting benefits under the Workers' Compensation Statutes. The lawsuit seeks injunctive relief and actual and statutory damages, as well as recovery of attorney's fees and legal expenses. In April 2017, the Circuit Court granted the Company’s Motion for Judgment on the Pleadings. The Plaintiff has appealed the Circuit Court’s ruling to the Florida Second District Court of Appeal. The Company will vigorously defend the lawsuit. In December 2014, the Company received a Civil Investigative Demand issued pursuant to the U.S. False Claims Act from the U.S. Attorney's Office for South Carolina, which requested information regarding alleged remuneration and services provided by the Company to physicians who also received draw and processing/handling fees from competitor laboratories Health Diagnostic Laboratory, Inc. (HDL) and Singulex, Inc. (Singulex). The Company cooperated with the request. On April 4, 2018, the U.S. District Court for the District of South Carolina, Beaufort Division, unsealed a False Claims Act lawsuit, United States of America ex rel. Scarlett Lutz, et al. v. Laboratory Corporation of America Holdings , which alleges that the Company's financial relationships with referring physicians violate federal and state anti-kickback statutes. The Plaintiffs' Fourth Amended Complaint further alleges that the Company conspired with HDL and Singulex in violation of the Federal False Claims Act and the California and Illinois insurance fraud prevention acts by facilitating HDL's and Singulex's offers of illegal inducements to physicians and the referral of patients to HDL and Singulex for laboratory testing. The lawsuit seeks actual and treble damages and civil penalties for each alleged false claim, as well as recovery of costs, attorney's fees, and legal expenses. Neither the U.S. government nor any state government has intervened in the lawsuit. The Company will vigorously defend the lawsuit. Prior to the Company's acquisition of Sequenom, Inc. (Sequenom) between August 15, 2016, and August 24, 2016, six putative class-action lawsuits were filed on behalf of purported Sequenom stockholders (captioned Malkoff v. Sequenom, Inc., et al., No. 16-cv-02054- JAH-BLM , Gupta v. Sequenom, Inc., et al ., No. 16-cv-02084-JAH-KSC, Fruchter v. Sequenom, Inc., et al ., No. 16-cv-02101- WQH-KSC, Asiatrade Development Ltd. v. Sequenom, Inc., et al. , No. 16-cv-02113-AJB-JMA, Nunes v. Sequenom, Inc., et al. , No. 16-cv-02128-AJB-MDD, and Cusumano v. Sequenom, Inc., et al. , No. 16-cv-02134-LAB-JMA) in the U.S. District Court for the Southern District of California challenging the acquisition transaction. The complaints asserted claims against Sequenom and members of its Board of Directors (the Individual Defendants). The Nunes action also named the Company and Savoy Acquisition Corp. (Savoy), a wholly owned subsidiary of the Company, as defendants. The complaints alleged that the defendants violated Sections 14(e), 14(d)(4) and 20 of the Securities Exchange Act of 1934 by failing to disclose certain allegedly material information. In addition, the complaints in the Malkoff action, Asiatrade action, and the Cusumano action alleged that the Individual Defendants breached their fiduciary duties to Sequenom shareholders. The actions sought, among other things, injunctive relief enjoining the merger. On August 30, 2016, the parties entered into a Memorandum of Understanding (MOU) in each of the above-referenced actions. On September 6, 2016, the Court entered an order consolidating for all pre-trial purposes the six individual actions described above under the caption In re Sequenom, Inc. Shareholder Litig. , Lead Case No. 16-cv-02054-JAH-BLM, and designating the complaint from the Malkoff action as the operative complaint for the consolidated action. On November 11, 2016, two competing motions were filed by two separate stockholders (James Reilly and Shikha Gupta) seeking appointment as lead plaintiff under the terms of the Private Securities Litigation Reform Act of 1995. On June 7, 2017, the Court entered an order declaring Mr. Reilly as the lead plaintiff and approving Mr. Reilly's selection of lead counsel. The parties agree that the MOU has been terminated. The Plaintiffs filed a Consolidated Amended Class Action Complaint on July 24, 2017, and the Defendants filed a Motion to Dismiss, which remains pending. The Company will vigorously defend the lawsuit. On August 3, 2016, the Company was served with a putative class action lawsuit, Daniel L. Bloomquist v. Covance Inc., et al. , filed in the Superior Court of California, County of San Diego. The Complaint alleges that Covance Inc. violated the California Labor Code and California Business & Professions Code by failing to provide overtime wages, failing to provide meal and rest periods, failing to pay for all hours worked, failing to pay for all wages owed upon termination, and failing to provide accurate itemized wage statements to Clinical Research Associates and Senior Clinical Research Associates employed by Covance in California. The lawsuit seeks monetary damages, civil penalties, injunctive relief, and recovery of attorney's fees and costs. On October 13, 2016, the case was removed to the U.S. District Court for the Southern District of California. On May 3, 2017, the U.S. District Court for the Southern District of California remanded the case back to the Superior Court. The Company will vigorously defend the lawsuit. On February 7, 2017, Sequenom received a subpoena from the SEC relating to an SEC investigation into the trading activity of Sequenom shares in connection with the Company's July 2016 announcement regarding the Sequenom merger. On March 7, 2017, the Company received a similar subpoena. The Company is cooperating with these requests. On March 10, 2017, the Company was served with a putative class action lawsuit, Victoria Bouffard, et al. v. Laboratory Corporation of America Holdings , filed in the U.S. District Court for the Middle District of North Carolina. The complaint alleges that the Company's patient list prices unlawfully exceed the rates negotiated for the same services with private and public health insurers in violation of various state consumer protection laws. The lawsuit also alleges breach of implied contract or quasi-contract, unjust enrichment, and fraud. The lawsuit seeks statutory, exemplary, and punitive damages, injunctive relief, and recovery of attorney's fees and costs. In May 2017, the Company filed a Motion to Dismiss Plaintiffs' Complaint and Strike Class Allegations; the Motion to Dismiss was granted in March 2018 without prejudice. On October 10, 2017, a second putative class action lawsuit, Sheryl Anderson, et al. v. Laboratory Corporation of America Holdings , was filed in the U.S. District Court for the Middle District of North Carolina. The complaint contained similar allegations and sought similar relief to the Bouffard complaint, and added additional counts regarding state consumer protection laws. On August 10, 2018, the Plaintiffs filed an Amended Complaint, which consolidated the Bouffard and Anderson actions. On September 10, 2018, the Company filed a Motion to Dismiss Plaintiffs’ Amended Complaint and Strike Class Allegations, which remains pending. The Company will vigorously defend the lawsuits. On August 1, 2017, the Company was served with a putative class action lawsuit, Maria T. Gonzalez, et al. v. Examination Management Services, Inc. and Laboratory Corporation of America Holdings, filed in the U.S. District Court for the Southern District of California. The complaint alleges that the Company misclassified phlebotomists as independent contractors through an arrangement with the co-Defendant temporary staffing agency. The complaint further alleges that the Company violated the California Labor Code and California Business and Professions Code by failing to pay minimum wage, failing to pay for all hours worked, failing to pay for all wages owed upon termination, and failing to provide accurate itemized wage statements. The lawsuit seeks monetary damages, civil penalties, injunctive relief, and recovery of attorney's fees and costs. The parties have reached a tentative settlement subject to Court approval. A hearing on the settlement is scheduled for November 8, 2018. On September 7, 2017, the Company was served with a putative class action lawsuit, John Sealock, et al. v. Covance Market Access Services, Inc ., filed in the U.S. District Court for the Southern District of New York. The complaint alleges that Covance Market Access Services, Inc. violated the Fair Labor Standards Act and New York labor laws by failing to provide overtime wages, failing to pay for all hours worked, and failing to provide accurate wage statements. The lawsuit seeks monetary damages, civil penalties, injunctive relief, and recovery of attorney's fees and costs. In November 2017, the Company filed a Motion to Strike Class Allegations, which was denied. In December 2017, the Plaintiff filed a Motion for Conditional Certification of a Collective Action, which was granted in May 2018. The Company will vigorously defend the lawsuit. On November 6, 2017, Covance was served with two False Claims Act lawsuits, Health Choice Alliance, LLC on behalf of the United States of America, et al. v. Eli Lilly and Company, Inc. et al. , and Health Choice Advocates, LLC, on behalf of the United States of America v. Gilead Sciences, Inc., et al. , both filed in the U.S. District Court for the Eastern District of Texas. The complaints allege that under the Federal False Claims Act and various state analogues Covance and the co-defendants unlawfully provided in-kind remuneration to medical providers in the form of reimbursement support services in order to induce providers to prescribe certain drugs. Neither the U.S. government nor any state government intervened in the lawsuits. The lawsuits seek actual and treble damages and civil penalties for each alleged false claim, as well as recovery of costs. The Company’s Motion to Dismiss was filed in both cases in February 2018. On July 23, 2018, Plaintiffs in the Gilead case filed a Motion for Voluntary Dismissal Without Prejudice which the Court granted on July 27, 2018. On August 10, 2018, the Court in the Lilly case entered an Order granting in part and denying in part without prejudice the Defendants’ Motions to Dismiss. On September 12, 2018, Plaintiffs in the Lilly case filed a Second Amended Complaint, which included additional allegations related to the same conduct alleged in the previous complaint. The Company will vigorously defend the lawsuits. On March 6, 2018, the Company was served with a lawsuit arising under the California Labor Code Private Attorney General Act (LCPAGA), Agnes Austria and Josephine Hoelscher v. Laboratory Corporation of America Holdings, et al. , filed in the Superior Court of California, County of San Diego. Plaintiffs allege that they were improperly classified as exempt employees and, therefore, allege that they were not properly paid overtime compensation, meal and rest break premiums, did not receive compliant wage statements, and were not properly paid wages upon termination of employment. Plaintiffs assert these actions violate various Labor Code provisions and constitute an unfair competition practice under California law. The parties reached a settlement that was approved by the Court, by Order dated September 14, 2018. On April 2, 2018, the Company was served with a putative class action lawsuit, Craig Cunningham, et al. v. Laboratory Corporation of America Holdings d/b/a LabCorp , filed in the U.S. District Court for the Middle District of North Carolina. The lawsuit alleges that the Company violated the TCPA by contacting Plaintiff at least twice on his cell phone without his prior consent using a prerecorded or artificial voice. The lawsuit seeks actual damages for each violation, subject to trebling under the TCPA, and injunctive relief. The parties have reached a settlement in principle. On July 16, 2018, the Company reported that it had detected suspicious activity on its information technology network and was taking steps to respond to and contain the activity. The activity was subsequently determined to be a new variant of ransomware affecting certain LCD information technology systems. In response, the Company took certain systems offline which temporarily affected test processing and customer access to test results, and also affected certain other information technology systems involved in conducting Company-wide operations. To date, the Company has not been the subject of any legal proceedings involving this incident, but it is possible that the Company could be the subject of claims from persons alleging they suffered damages from the incident, or actions by governmental authorities. The Company cooperated with law enforcement and regulatory authorities with respect to the incident. On September 10, 2018, the Company was served with a LCPAGA lawsuit, Terri Wilson v. Laboratory Corporation of America Holdings , which was filed in the U.S. District Court for the Northern District of California. Plaintiff alleges claims for failure to pay meal and rest break premiums, failure to provide compliant wage statements, failure to compensate employees for all hours worked, and failure to pay wages upon termination of employment. Plaintiff asserts these actions violate various Labor Code provisions and constitute an unfair competition practice under California law. The lawsuit seeks monetary damages, civil penalties, injunctive relief, and recovery of attorney's fees and costs. The Company will vigorously defend the lawsuit. On September 21, 2018, the Company was served with a putative class action lawsuit, Alma Haro v. Laboratory Corporation of America et al. , which was filed in the Superior Court of California, County of Los Angeles. Plaintiff alleges that employees were not properly paid overtime compensation, minimum wages, meal and rest break premiums, did not receive compliant wage statements, and were not properly paid wages upon termination of employment. Plaintiff asserts these actions violate various Labor Code provisions and constitute an unfair competition practice under California law. The lawsuit seeks monetary damages, civil penalties, and recovery of attorney's fees and costs. The Company will vigorously defend the lawsuit. On December 11, 2017, the American Clinical Laboratory Association (ACLA) filed a lawsuit captioned ACLA v. Azar in the U.S. District Court for the District of Columbia to challenge the methodology used by the Department of Health and Human Services in implementing certain aspects of the PAMA legislation. On September 21, 2018, the court entered a Memorandum Opinion dismissing the lawsuit for lack of subject matter jurisdiction. On October 19, 2018, ACLA filed a notice of appeal with respect to that order. Under the Company's present insurance programs, coverage is obtained for catastrophic exposure as well as those risks required to be insured by law or contract. The Company is responsible for the uninsured portion of losses related primarily to general, professional and vehicle liability, certain medical costs and workers' compensation. The self-insured retentions are on a per-occurrence basis without any aggregate annual limit. Provisions for losses expected under these programs are recorded based upon the Company's estimates of the aggregated liability of claims incurred. As of September 30, 2018 , the Company had provided letters of credit aggregating approximately $72.2 , primarily in connection with certain insurance programs. The Company's availability under its revolving credit facility is reduced by the amount of these letters of credit.

PENSION AND POSTRETIREMENT PLAN

PENSION AND POSTRETIREMENT PLANS	9 Months Ended
	Sep. 30, 2018
Postemployment Benefits [Abstract]
Pension And Postretirement Plans	PENSION AND POST-RETIREMENT PLANS The Company’s defined contribution retirement plan (401K Plan) covers substantially all legacy LabCorp employees. All employees eligible for the 401K Plan receive a minimum 3% non-elective contribution concurrent with each payroll period. The 401K Plan also permits discretionary contributions by the Company of up to 1% and up to 3% of pay for eligible employees based on years of service with the Company. The cost of this plan was $17.3 and $14.9 for the three months ended September 30, 2018 , and 2017 , respectively, and was $49.1 and $43.6 during the nine months ended September 30, 2018 , and 2017 , respectively. As a result of the Covance acquisition, the Company also incurred expense of $16.3 and $14.0 for the Covance 401K plan during the three months ended September 30, 2018 , and 2017 , respectively, and $51.6 and $42.6 during the nine months ended September 30, 2018 , and 2017 , respectively. All of the Covance U.S. employees, excluding legacy Chiltern employees, are eligible to participate in the Covance 401K plan, which features a maximum 4.5% Company match, based upon a percentage of the employee’s contributions. Chiltern employees are eligible to participate in the Chiltern 401K plan, which features a maximum 3.0% Company match, based upon a percentage of the employee's contributions. The Company also maintains a frozen defined benefit retirement plan (Company Plan), which as of December 31, 2009, covered substantially all employees. The benefits to be paid under the Company Plan are based on years of credited service through December 31, 2009, and ongoing interest credits. Effective January 1, 2010, the Company Plan was closed to new participants. The Company’s policy is to fund the Company Plan with at least the minimum amount required by applicable regulations. The Company maintains a second, unfunded, non-contributory, non-qualified defined benefit retirement plan (PEP), which as of December 31, 2009, covered substantially all of its senior management group. The PEP supplements the Company Plan and was closed to new participants effective January 1, 2010. The effect on operations for the Company Plan and the PEP is summarized as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 1.3 $ 1.4 $ 3.9 $ 4.2 Interest cost on benefit obligation 3.3 3.6 9.8 10.8 Expected return on plan assets (4.1 ) (4.1 ) (12.3 ) (12.3 ) Net amortization and deferral 2.9 2.8 8.8 8.3 Defined benefit plan costs $ 3.4 $ 3.7 $ 10.2 $ 11.0 During the three and nine months ended September 30, 2018 , the Company contributed $25.3 and $27.1 , respectively, to the Company Plan. As a result of the Covance acquisition, the Company also has a frozen non-qualified Supplemental Executive Retirement Plan (SERP). The SERP, which is not funded, is intended to provide retirement benefits for certain executive officers of the Company who were formerly employees of Covance. Benefit amounts are based upon years of service and compensation of the participating employees. The components of the net periodic pension cost for the three and nine months ended September 30, 2018 , and 2017, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest cost $ 0.1 $ 0.1 $ 0.1 $ 0.2 Settlement gain — (0.1 ) — (0.3 ) Net periodic pension cost $ 0.1 $ — $ 0.1 $ (0.1 ) The Company has assumed the obligations under a subsidiary’s post-retirement medical plan. Coverage under this plan is restricted to a limited number of employees/retirees of the subsidiary. The Company funds the plan through monthly contributions to a Health Reimbursement Arrangement, which can be used by eligible participants to purchase health care insurance through insurance exchanges. Effective January 1, 2017, Health Reimbursement Arrangement contributions for Medicare eligible participants ceased. The effect on operations of the post-retirement medical plan is shown in the following table: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest cost on benefit obligation $ 0.1 $ 0.1 0.2 0.3 Net amortization and deferral (0.4 ) (1.7 ) (1.0 ) (5.1 ) Post-retirement medical plan benefits $ (0.3 ) $ (1.6 ) $ (0.8 ) $ (4.8 ) Also as a result of the Covance acquisition, the Company sponsors a post-employment retiree health and welfare plan for the benefit of eligible retirees at certain U.S. subsidiaries who retire after satisfying service and age requirements. Effective January 1, 2017, this plan ceased directly providing medical, prescription drug and dental coverage options previously available to eligible participants. Instead, the Company will fund the plan through monthly contributions to a Health Reimbursement Arrangement, which can be used by non-Medicare eligible participants to purchase health care insurance through insurance exchanges. The net periodic post-retirement benefit cost for the three months ended September 30, 2018 , and 2017 , was $(0.1) and $0.5 , respectively, and was $(0.3) and $1.5 for the nine months ended September 30, 2018 , and 2017 , respectively. As a result of the Covance acquisition, the Company sponsors two defined benefit pension plans for the benefit of its employees at two U.K. subsidiaries and one defined benefit pension plan for the benefit of its employees at a German subsidiary, all of which are legacy plans of previously acquired companies. Benefit amounts for all three plans are based upon years of service and compensation. The German plan is unfunded while the U.K. pension plans are funded. The Company’s funding policy has been to contribute annually amounts at least equal to the local statutory funding requirements. U.K. Plans Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 0.9 $ 1.0 $ 2.7 $ 2.8 Interest cost on benefit obligation 1.8 1.9 5.7 5.6 Expected return on plan assets (3.1 ) (2.9 ) (9.7 ) (8.5 ) Net (gain) from prior periods — 0.2 — 0.5 Defined benefit plan costs $ (0.4 ) $ 0.2 $ (1.3 ) $ 0.4 Assumptions used to determine defined benefit plan cost Discount rate 2.5 % 2.7 % 2.5 % 2.7 % Expected return on assets 4.5 % 4.7 % 4.5 % 4.7 % Salary increases 3.6 % 3.8 % 3.6 % 3.8 % German Plan Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 0.3 $ 0.3 $ 0.9 $ 0.8 Interest cost on benefit obligation 0.1 0.1 0.5 0.4 Defined benefit plan costs $ 0.4 $ 0.4 $ 1.4 $ 1.2 Assumptions used to determine defined benefit plan cost Discount rate 1.7 % 1.7 % 1.7 % 1.7 % Expected return on assets N/A N/A N/A N/A Salary increases 2.0 % 2.0 % 2.0 % 2.0 %

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The Company’s population of financial assets and liabilities subject to fair value measurements as of September 30, 2018 , and December 31, 2017 , is as follows: Fair Value Measurements as of Fair Value as of September 30, 2018 Balance Sheet Using Fair Value Hierarchy Classification September 30, 2018 Level 1 Level 2 Level 3 Noncontrolling interest put Noncontrolling interest $ 15.9 $ — $ 15.9 $ — Interest rate swap Other liabilities 0.5 — 0.5 — Cross currency swap asset Other assets, net 8.1 — 8.1 — Cash surrender value of life insurance policies Other assets, net 69.7 — 69.7 — Deferred compensation liability Other liabilities 71.1 — 71.1 — Contingent consideration Other liabilities 16.5 — — 16.5 Fair Value Measurements as of Fair Value as of December 31, 2017 Balance Sheet Using Fair Value Hierarchy Classification December 31, 2017 Level 1 Level 2 Level 3 Noncontrolling interest put Noncontrolling interest $ 16.3 $ — $ 16.3 $ — Interest rate swap Other assets, net 4.1 — 4.1 — Cash surrender value of life insurance policies Other assets, net 64.0 — 64.0 — Deferred compensation liability Other liabilities 64.5 — 64.5 — Contingent consideration Other liabilities 16.5 — — 16.5 The Company has a noncontrolling interest put related to its Ontario subsidiary that has been classified as mezzanine equity in the Company’s condensed consolidated balance sheets. The noncontrolling interest put is valued at its contractually determined value, which approximates fair value. The Company offers certain employees the opportunity to participate in an employee-funded deferred compensation plan (DCP). A participant's deferrals are allocated by the participant to one or more of 22 measurement funds, which are indexed to externally managed funds. From time to time, to offset the cost of the growth in the participant's investment accounts, the Company purchases life insurance policies, with the Company named as beneficiary of the policies. Changes in the cash surrender value of these policies are based upon earnings and changes in the value of the underlying investments, which are typically invested in a manner similar to the participants' allocations. Changes in the fair value of the DCP obligation are derived using quoted prices in active markets based on the market price per unit multiplied by the number of units. The cash surrender value and the DCP obligations are classified within Level 2 because their inputs are derived principally from observable market data by correlation to the hypothetical investments. The Company has contingent accrued earn-out business acquisition consideration liabilities which were recorded at fair value on the acquisition date and are remeasured quarterly based on the then assessed fair value and adjusted if necessary. The increases or decreases in the fair value of contingent consideration payable can result from changes in anticipated revenue levels and changes in assumed discount periods and rates. As the fair value measure is based on significant inputs that are not observable in the market, they are categorized as Level 3. The carrying amounts of cash and cash equivalents, accounts receivable, income taxes receivable, and accounts payable are considered to be representative of their respective fair values due to their short-term nature. The fair market value of the zero-coupon subordinated notes, based on market pricing, was approximately $20.3 and $18.8 as of September 30, 2018 , and December 31, 2017 , respectively. The fair market value of all of the senior notes, based on market pricing, was approximately $5,904.8 and $6,078.9 as of September 30, 2018 , and December 31, 2017 , respectively. The Company's note and debt instruments are classified as Level 2 instruments, as the fair market values of these instruments are determined using other observable inputs.

DERIVATIVE INSTRUMENTS AND HEDG

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments And Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES The Company addresses its exposure to market risks, principally the market risk associated with changes in interest rates and foreign currency exchange rates, through a controlled program of risk management that includes, from time to time, the use of derivative financial instruments such as interest rate and cross currency swap agreements (see Interest Rate Swap and Cross Currency Swap sections below). Although the Company’s zero-coupon subordinated notes contain features that are considered to be embedded derivative instruments (see Embedded Derivatives Related to the Zero-Coupon Subordinated Notes section below), the Company does not hold or issue derivative financial instruments for trading purposes. The derivative financial instrument contracts are with major investment grade financial institutions and the Company does not anticipate any material non-performance by any of the counterparties. The Company does not believe that its exposure to market risk is material to the Company’s financial position or results of operations. Interest Rate Swap The Company is party to two fixed-to-variable interest rate swap agreements for its 4.625% senior notes due 2020 with an aggregate notional amount of $600.0 and variable interest rates based on one-month LIBOR plus 2.298% to hedge against changes in the fair value of a portion of the Company's long term debt. These derivative financial instruments are accounted for as fair value hedges of the senior notes due 2020. These interest rate swaps are included in other long-term assets or other long-term liabilities, as applicable, and added to or subtracted from the value of the senior notes, with an aggregate fair value of $ 0.5 (liability) and $4.1 (asset) at September 30, 2018 , and December 31, 2017 , respectively. As the specific terms and notional amounts of the derivative financial instruments match those of the fixed-rate debt being hedged, the derivative instruments are assumed to be perfectly effective hedges and accordingly, there is no impact to the Company's consolidated statements of operations. Cross Currency Swap During the first quarter of 2018, the Company entered into six USD to Swiss Franc cross-currency swap agreements with an aggregate notional value of $600.0 and which are accounted for as a hedge against its net investment in a Swiss subsidiary. Of the notional value, $300.0 matures in 2022 and $300.0 matures in 2025. These cross currency swaps maturing in 2022 and 2025 are included in other long-term assets with an aggregate fair value of $6.6 and $1.5 , respectively, as of September 30, 2018 . Changes in the fair value of the cross-currency swaps are charged or credited through accumulated other comprehensive income in the Consolidated Balance Sheet until the hedged item is recognized in earnings. The cumulative amount of the fair value hedging adjustment included in the current value of the cross currency swaps is $(16.1) and $8.1 for the three and nine months ended September 30, 2018 , respectively, and was recognized as currency translation within the Consolidated Statement of Comprehensive Earnings. There were no amounts reclassified from the Consolidated Statement of Comprehensive Earnings to the Consolidated Statement of Operations during the three or nine months ended September 30, 2018. Embedded Derivatives Related to the Zero-Coupon Subordinated Notes The Company’s zero-coupon subordinated notes contain the following two features that are considered to be embedded derivative instruments under authoritative guidance in connection with accounting for derivative instruments and hedging activities: 1) The Company will pay contingent cash interest on the zero-coupon subordinated notes after September 11, 2006, if the average market price of the notes equals 120% or more of the sum of the issue price, accrued original issue discount and contingent additional principal, if any, for a specified measurement period. 2) Holders may surrender zero-coupon subordinated notes for conversion during any period in which the rating assigned to the zero-coupon subordinated notes by Standard & Poor’s Ratings Services is BB- or lower. The Company believes these embedded derivatives had no fair value at September 30, 2018 , and December 31, 2017 . These embedded derivatives also had no impact on the condensed consolidated statements of operations for the nine months ended September 30, 2018 , and 2017 , respectively. Other Derivative Instruments The Company periodically enters into foreign currency forward contracts, which are recognized as assets or liabilities at their fair value. These contracts do not qualify for hedge accounting and the changes in fair value are recorded directly to earnings. The contracts are short-term in nature and the fair value of these contracts is based on market prices for comparable contracts. The fair value of these contracts is not significant as of September 30, 2018 , and December 31, 2017 .

SUPPLEMENTAL CASH FLOW INFORMAT

SUPPLEMENTAL CASH FLOW INFORMATION	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Nine Months Ended September 30, 2018 2017 Supplemental schedule of cash flow information: Cash paid during period for: Interest $ 276.3 $ 174.4 Income taxes, net of refunds 235.0 263.7 Disclosure of non-cash financing and investing activities: Conversion of zero-coupon convertible debt 0.3 13.7 Assets acquired under capital leases — 7.3 Increase (decrease) in accrued property, plant and equipment 6.9 (0.4 )
Supplemental Cash Flow Information	SUPPLEMENTAL CASH FLOW INFORMATION Nine Months Ended September 30, 2018 2017 Supplemental schedule of cash flow information: Cash paid during period for: Interest $ 276.3 $ 174.4 Income taxes, net of refunds 235.0 263.7 Disclosure of non-cash financing and investing activities: Conversion of zero-coupon convertible debt 0.3 13.7 Assets acquired under capital leases — 7.3 Increase (decrease) in accrued property, plant and equipment 6.9 (0.4 )

BUSINESS ACQUISITIONS

BUSINESS ACQUISITIONS	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	BUSINESS ACQUISITIONS AND DISPOSITIONS On September 1, 2017, the Company completed the acquisition of Chiltern International Group Limited (Chiltern), a specialty CRO, pursuant to a definitive agreement to acquire all of the share capital of Chiltern, in an all-cash transaction valued at approximately $1,224.5 . The Company funded the acquisition through a combination of bank financing and the issuance of bonds. Chiltern is part of the Company's CDD segment. The final valuation of acquired assets and assumed liabilities as of September 1, 2017, include the following: Consideration Transferred Cash consideration $ 1,224.5 Net Assets Acquired Cash and cash equivalents $ 30.7 Accounts receivable 103.6 Unbilled services 32.6 Prepaid expenses and other 57.9 Property, plant and equipment 12.1 Goodwill 735.9 Customer relationships 602.0 Trade names and trademarks 10.6 Technology 26.0 Total assets acquired 1,612.3 Accounts payable 45.1 Accrued expenses and other 19.6 Unearned revenue 124.2 Deferred income taxes 196.5 Other liabilities 2.4 Total liabilities acquired 387.8 Net assets acquired $ 1,224.5 The amortization periods for intangible assets acquired are 21 years for customer relationships, 7 years for trade names and trademarks, and 9 years for technology. Unaudited Pro Forma Information The Company completed the Chiltern acquisition on September 1, 2017. Had the Chiltern acquisition been completed as of January 1, 2016, the Company's pro forma results would have been as follows: Three Months Ended September 30, 2017 Nine Months Ended Net revenues $ 2,747.3 $ 8,086.6 Operating income 313.2 975.0 Net income 158.1 521.2 Earnings per share: Basic $ 1.55 $ 5.09 Diluted $ 1.52 $ 5.02 The unaudited pro forma results reflect certain adjustments related to past operating performance and acquisition accounting adjustments, such as increased amortization expense and decreased depreciation expense based on the estimated fair value of assets acquired, the impact of the Company’s new financing arrangements, and the related tax effects. The pro forma results do not include any anticipated synergies which may be achievable subsequent to the Chiltern acquisition. To produce the unaudited pro forma financial information, the Company adjusted Chiltern’s assets and liabilities to their estimated fair value based on a valuation as of September 1, 2017. These pro forma results of operations have been prepared for comparative purposes only, and they do not purport to be indicative of the results of operations that actually would have resulted had the acquisition of Chiltern occurred on the date indicated or that may result in the future. During the nine months ended September 30, 2018, the Company also acquired various businesses and related assets for approximately $79.1 in cash (net of cash acquired). The purchase consideration for all acquisitions year to date has been allocated to the estimated fair market value of the net assets acquired, including approximately $48.5 in identifiable intangible assets and a residual amount of goodwill of approximately $49.5 . These acquisitions were made primarily to extend the Company's geographic reach in important market areas and/or enhance the Company's scientific differentiation. On April 30, 2018, the Company entered into a definitive agreement to sell the Food Solutions business, a global provider of innovative product design and product integrity services for end-user segments that span the global food supply chain, for an all-cash purchase price of $670.0 . The Company believes that the opportunities for creating lasting value from its laboratory diagnostic business, the CRO business, and the enterprise-wide combination of the two. In addition, the Company concluded that, given the competitive dynamics of the food testing market, Food Solutions would be unlikely to achieve sufficient scale to be a top global business. The sale of Food Solutions allows the Company to focus on its primary growth opportunities and at the same time better positions Food Solutions to serve the global food supply industry. The transaction closed on August 1, 2018, and a net gain of $258.3 was recorded in Other, net in the consolidated statement of operations. Total assets and total liabilities held for sale for the Food Solutions business as of December 31, 2017, include the following: December 31, 2017 Assets: Cash and cash equivalents $ 0.1 Accounts receivable 24.4 Unbilled services 7.6 Supplies inventories 0.4 Prepaid expenses and other 1.2 Property, plant and equipment, net 42.3 Goodwill, net 170.5 Intangible assets, net 174.7 Other assets, net 0.3 Total assets held for sale $ 421.5 Liabilities: Accounts payable $ 2.4 Accrued expenses and other 15.2 Unearned revenue 2.6 Deferred income taxes and other tax liabilities 64.1 Other liabilities 2.2 Total liabilities held for sale $ 86.5 Net assets held for sale $ 335.0 The Company also divested its forensic testing services business in the U.K. on August 7, 2018, resulting in a loss of $48.9 recorded in Other, net in the consolidated statement of operations. Operating income for the divested businesses was $2.4 and $6.1 , for the three and nine months ended September 30, 2018, (which includes divested operations through their respective disposal dates in early August) and $2.2 and $10.3 , for the three and nine months ended September 30, 2017.

BUSINESS SEGMENT INFORMATION Bu

BUSINESS SEGMENT INFORMATION Business Segment information (Notes)	9 Months Ended
	Sep. 30, 2018
Segment Reporting Information [Line Items]
Segment Reporting Disclosure [Text Block]	BUSINESS SEGMENT INFORMATION The following table is a summary of segment information for the three and nine months ended September 30, 2018 , and 2017 . The management approach has been used to present the following segment information. This approach is based upon the way the management of the Company organizes its business unit operations for making operating decisions and assessing performance. Financial information is reported on the basis that it is used internally by the chief operating decision maker (CODM) for evaluating segment performance and deciding how to allocate resources to segments. The Company’s chief executive officer has been identified as the CODM. Segment asset information is not presented because it is not used by the CODM at the segment level. Operating earnings of each segment represents net revenues less directly identifiable expenses to arrive at operating income for the segment. General management and administrative corporate expenses are included in general corporate expenses below. The table below represents information about the Company’s reporting segments for the three and nine months ended September 30, 2018 , and 2017 : Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Revenues: LCD $ 1,752.0 $ 1,754.7 $ 5,336.3 $ 5,115.5 CDD 1,081.5 867.1 3,214.1 2,448.7 Intercompany eliminations (2.2 ) (0.4 ) (4.5 ) (0.9 ) Revenues 2,831.3 2,621.4 8,545.9 7,563.3 Operating earnings: LCD 289.4 336.6 929.2 982.0 CDD 87.9 28.0 195.3 97.8 Unallocated corporate expenses (33.9 ) (37.9 ) (106.5 ) (105.2 ) Total operating income 343.4 326.7 1,018.0 974.6 Other income (expense), net 156.2 (59.9 ) 35.8 (163.3 ) Earnings before income taxes 499.6 266.8 1,053.8 811.3 Provision for income taxes 180.6 92.5 328.1 268.6 Net earnings 319.0 174.3 725.7 542.7 Less (earnings) loss attributable to noncontrolling interests (0.2 ) (2.8 ) 0.1 (3.4 ) Net income attributable to Laboratory Corporation of America Holdings $ 318.8 $ 171.5 $ 725.8 $ 539.3

BASIS OF FINANCIAL STATEMENT _2

BASIS OF FINANCIAL STATEMENT PRESENTATION Restated Financial Statements (Tables)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Restatement to Prior Year Income [Table Text Block]		Adoption of the standards related to revenue recognition, pension accounting and cash receipts and payments as well as the revision for payments made to tax authorities for withheld shares from equity awards impacted previously reported results as follows: Condensed Consolidated Statement of Operations For the Three Months Ended September 30, 2017 As Previously Reported ASC 606 Revenue Adjustments Pension Adjustments As Adjusted Total revenues $ 2,655.2 $ (33.8 ) $ — $ 2,621.4 Total cost of revenue 1,772.4 64.6 0.2 1,837.2 Gross profit 882.8 (98.4 ) (0.2 ) 784.2 Selling, general and administrative expenses 465.3 (84.5 ) 0.5 381.3 Other operating and non-operating expenses, net 136.4 0.4 (0.7 ) 136.1 Provision for income taxes 97.7 (5.2 ) — 92.5 Net earnings 183.4 (9.1 ) — 174.3 Less: Net earnings attributable to noncontrolling interest (2.8 ) — — (2.8 ) Net earnings attributable to Laboratory Corporation of America Holdings $ 180.6 $ (9.1 ) $ — $ 171.5 Basic earnings per share $ 1.77 $ 1.68 Diluted earnings per share $ 1.74 $ 1.65 Condensed Consolidated Statement of Operations For the Nine Months Ended September 30, 2017 As previously reported ASC 606 Revenue Adjustments Pension Adjustments As Adjusted Total revenues $ 7,645.1 $ (81.8 ) $ — $ 7,563.3 Total cost of revenue 5,096.9 191.3 0.4 5,288.6 Gross profit 2,548.2 (273.1 ) (0.4 ) 2,274.7 Selling, general and administrative expenses 1,320.0 (239.4 ) 1.3 1,081.9 Other operating and non-operating expenses, net 382.3 0.9 (1.7 ) 381.5 Provision for income taxes 281.1 (12.5 ) — 268.6 Net earnings 564.8 (22.1 ) — 542.7 Less: Net earnings attributable to noncontrolling interest (3.4 ) — — (3.4 ) Net earnings attributable to Laboratory Corporation of America Holdings $ 561.4 $ (22.1 ) $ — $ 539.3 Basic earnings per share $ 5.48 $ 5.27 Diluted earnings per share $ 5.40 $ 5.19 Condensed Consolidated Statement of Cash Flows For the Nine Months Ended September 30, 2017 As Previously Reported Tax Payments for Equity Awards Revision ASC 606 Revenue Adjustments Zero-Coupon Notes Adjustments As Adjusted Net cash provided by operating activities $ 895.3 $ 46.5 $ — $ (8.7 ) $ 933.1 Net cash used for investing activities (2,050.4 ) — — — (2,050.4 ) Net cash provided by financing activities 1,111.3 (46.5 ) — 8.7 1,073.5 Effect of exchange rate changes on cash and cash equivalents 19.4 — (0.1 ) — 19.3 Net decrease in cash and cash equivalents $ (24.4 ) $ (24.5 )
Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]	Condensed Consolidated Balance Sheets December 31, 2017 As Previously Reported ASC 606 Revenue Adjustments As Adjusted Current assets $ 2,682.6 $ 51.2 $ 2,733.8 Long-term assets 13,885.4 53.8 13,939.2 Total assets $ 16,568.0 $ 105.0 $ 16,673.0 Current liabilities $ 2,046.1 $ 139.6 $ 2,185.7 Long-term liabilities 7,671.1 (8.7 ) 7,662.4 Noncontrolling interest 20.8 — 20.8 Shareholders' equity 6,830.0 (25.9 ) 6,804.1 Total liabilities and shareholders' equity $ 16,568.0 $ 105.0 $ 16,673.0

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Reconciliation of Basic earnings per Share to Diluted Earnings per Share	The following represents a reconciliation of basic earnings per share to diluted earnings per share: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Earnings Shares Per Share Amount Earnings Shares Per Share Amount Earnings Shares Per Share Amount Earnings Shares Per Share Amount Basic earnings per share: Net earnings $ 318.8 101.6 $ 3.14 $ 171.5 102.2 $ 1.68 $ 725.8 101.8 $ 7.13 $ 539.3 102.4 $ 5.27 Dilutive effect of employee stock options and awards — 1.0 — 1.4 — 1.2 — 1.4 Effect of convertible debt — 0.1 — 0.1 — 0.1 — 0.1 Diluted earnings per share: Net earnings including impact of dilutive adjustments $ 318.8 102.7 $ 3.10 $ 171.5 103.7 $ 1.65 $ 725.8 $ 103.1 $ 7.04 $ 539.3 $ 103.9 $ 5.19
Potential common shares not included in computation of diluted earnings per share	The following table summarizes the potential common shares not included in the computation of diluted earnings per share because their impact would have been antidilutive: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Stock options 0.1 0.1 0.1 0.1

RESTRUCTURING AND OTHER SPECI_2

RESTRUCTURING AND OTHER SPECIAL CHARGES Restructuring and Other Special Charges Detail (Tables)	9 Months Ended
	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Schedule of Restructuring Reserve by Type of Cost [Table Text Block]	The following represents the Company’s restructuring reserve activities for the period indicated: LCD CDD Severance and Other Employee Costs Lease and Other Facility Costs Severance and Other Employee Costs Lease and Other Facility Costs Total Balance as of December 31, 2017 $ 1.7 $ 10.1 $ 8.3 $ 34.6 $ 54.7 Restructuring charges 10.7 3.0 19.3 5.8 38.8 Reduction of prior restructuring accruals — (0.5 ) (1.2 ) (0.6 ) (2.3 ) Cash payments and other adjustments (11.1 ) (5.3 ) (16.3 ) (10.4 ) (43.1 ) Balance as of September 30, 2018 $ 1.3 $ 7.3 $ 10.1 $ 29.4 $ 48.1 Current $ 22.6 Non-current 25.5 $ 48.1

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the nine-month period ended September 30, 2018 , and for the year ended December 31, 2017 , are as follows: LCD CDD Total September 30, December 31, 2017 September 30, December 31, 2017 September 30, December 31, 2017 Balance as of January 1 $ 3,673.9 $ 3,644.8 $ 3,727.0 $ 2,779.6 $ 7,400.9 $ 6,424.4 Goodwill acquired during the period 3.9 198.5 45.6 811.3 49.5 1,009.8 Reclassification of goodwill as held for sale — (170.5 ) — — — (170.5 ) Dispositions (24.1 ) — — — (24.1 ) — Adjustments to goodwill (4.2 ) 1.1 (59.4 ) 136.1 (63.6 ) 137.2 Balance at end of period $ 3,649.5 $ 3,673.9 $ 3,713.2 $ 3,727.0 $ 7,362.7 $ 7,400.9
Schedule of Intangible Assets and Goodwill [Table Text Block]	The components of identifiable intangible assets are as follows: September 30, 2018 December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Customer relationships $ 4,115.7 $ (1,106.5 ) $ 3,009.2 $ 4,118.1 $ (992.8 ) $ 3,125.3 Patents, licenses and technology 454.6 (207.8 ) 246.8 457.9 (188.6 ) 269.3 Non-compete agreements 75.8 (53.0 ) 22.8 75.8 (48.3 ) 27.5 Trade names 405.0 (183.3 ) 221.7 407.9 (167.9 ) 240.0 Land use right 10.8 (3.7 ) 7.1 10.8 (2.5 ) 8.3 Canadian licenses 483.3 — 483.3 495.7 — 495.7 $ 5,545.2 $ (1,554.3 ) $ 3,990.9 $ 5,566.2 $ (1,400.1 ) $ 4,166.1

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Company's population of financial assets and liabilities subject to fair value measurements	The Company’s population of financial assets and liabilities subject to fair value measurements as of September 30, 2018 , and December 31, 2017 , is as follows: Fair Value Measurements as of Fair Value as of September 30, 2018 Balance Sheet Using Fair Value Hierarchy Classification September 30, 2018 Level 1 Level 2 Level 3 Noncontrolling interest put Noncontrolling interest $ 15.9 $ — $ 15.9 $ — Interest rate swap Other liabilities 0.5 — 0.5 — Cross currency swap asset Other assets, net 8.1 — 8.1 — Cash surrender value of life insurance policies Other assets, net 69.7 — 69.7 — Deferred compensation liability Other liabilities 71.1 — 71.1 — Contingent consideration Other liabilities 16.5 — — 16.5 Fair Value Measurements as of Fair Value as of December 31, 2017 Balance Sheet Using Fair Value Hierarchy Classification December 31, 2017 Level 1 Level 2 Level 3 Noncontrolling interest put Noncontrolling interest $ 16.3 $ — $ 16.3 $ — Interest rate swap Other assets, net 4.1 — 4.1 — Cash surrender value of life insurance policies Other assets, net 64.0 — 64.0 — Deferred compensation liability Other liabilities 64.5 — 64.5 — Contingent consideration Other liabilities 16.5 — — 16.5

SUPPLEMENTAL CASH FLOW INFORM_2

SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Nine Months Ended September 30, 2018 2017 Supplemental schedule of cash flow information: Cash paid during period for: Interest $ 276.3 $ 174.4 Income taxes, net of refunds 235.0 263.7 Disclosure of non-cash financing and investing activities: Conversion of zero-coupon convertible debt 0.3 13.7 Assets acquired under capital leases — 7.3 Increase (decrease) in accrued property, plant and equipment 6.9 (0.4 )
Supplemental Cash Flow Information	SUPPLEMENTAL CASH FLOW INFORMATION Nine Months Ended September 30, 2018 2017 Supplemental schedule of cash flow information: Cash paid during period for: Interest $ 276.3 $ 174.4 Income taxes, net of refunds 235.0 263.7 Disclosure of non-cash financing and investing activities: Conversion of zero-coupon convertible debt 0.3 13.7 Assets acquired under capital leases — 7.3 Increase (decrease) in accrued property, plant and equipment 6.9 (0.4 )

BUSINESS ACQUISITIONS Business

BUSINESS ACQUISITIONS Business Acquisitions Tables (Tables)	9 Months Ended
	Sep. 30, 2018
Business Acquisition [Line Items]
Disclosure of Long Lived Assets Held-for-sale [Table Text Block]	Total assets and total liabilities held for sale for the Food Solutions business as of December 31, 2017, include the following: December 31, 2017 Assets: Cash and cash equivalents $ 0.1 Accounts receivable 24.4 Unbilled services 7.6 Supplies inventories 0.4 Prepaid expenses and other 1.2 Property, plant and equipment, net 42.3 Goodwill, net 170.5 Intangible assets, net 174.7 Other assets, net 0.3 Total assets held for sale $ 421.5 Liabilities: Accounts payable $ 2.4 Accrued expenses and other 15.2 Unearned revenue 2.6 Deferred income taxes and other tax liabilities 64.1 Other liabilities 2.2 Total liabilities held for sale $ 86.5 Net assets held for sale $ 335.0
Business Acquisition, Pro Forma Information [Table Text Block]	The Company completed the Chiltern acquisition on September 1, 2017. Had the Chiltern acquisition been completed as of January 1, 2016, the Company's pro forma results would have been as follows: Three Months Ended September 30, 2017 Nine Months Ended Net revenues $ 2,747.3 $ 8,086.6 Operating income 313.2 975.0 Net income 158.1 521.2 Earnings per share: Basic $ 1.55 $ 5.09 Diluted $ 1.52 $ 5.02 The unaudited pro forma results reflect certain adjustments related to past operating performance and acquisition accounting adjustments, such as increased amortization expense and decreased depreciation expense based on the estimated fair value of assets acquired, the impact of the Company’s new financing arrangements, and the related tax effects. The pro forma results do not include any anticipated synergies which may be achievable subsequent to the Chiltern acquisition. To produce the unaudited pro forma financial information, the Company adjusted Chiltern’s assets and liabilities to their estimated fair value based on a valuation as of September 1, 2017. These pro forma results of operations have been prepared for comparative purposes only, and they do not purport to be indicative of the results of operations that actually would have resulted had the acquisition of Chiltern occurred on the date indicated or that may result in the future.
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	The final valuation of acquired assets and assumed liabilities as of September 1, 2017, include the following: Consideration Transferred Cash consideration $ 1,224.5 Net Assets Acquired Cash and cash equivalents $ 30.7 Accounts receivable 103.6 Unbilled services 32.6 Prepaid expenses and other 57.9 Property, plant and equipment 12.1 Goodwill 735.9 Customer relationships 602.0 Trade names and trademarks 10.6 Technology 26.0 Total assets acquired 1,612.3 Accounts payable 45.1 Accrued expenses and other 19.6 Unearned revenue 124.2 Deferred income taxes 196.5 Other liabilities 2.4 Total liabilities acquired 387.8 Net assets acquired $ 1,224.5

BUSINESS SEGMENT INFORMATION (T

BUSINESS SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reconciliation of Operating Income to Consolidated [Abstract]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block]	The table below represents information about the Company’s reporting segments for the three and nine months ended September 30, 2018 , and 2017 : Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Revenues: LCD $ 1,752.0 $ 1,754.7 $ 5,336.3 $ 5,115.5 CDD 1,081.5 867.1 3,214.1 2,448.7 Intercompany eliminations (2.2 ) (0.4 ) (4.5 ) (0.9 ) Revenues 2,831.3 2,621.4 8,545.9 7,563.3 Operating earnings: LCD 289.4 336.6 929.2 982.0 CDD 87.9 28.0 195.3 97.8 Unallocated corporate expenses (33.9 ) (37.9 ) (106.5 ) (105.2 ) Total operating income 343.4 326.7 1,018.0 974.6 Other income (expense), net 156.2 (59.9 ) 35.8 (163.3 ) Earnings before income taxes 499.6 266.8 1,053.8 811.3 Provision for income taxes 180.6 92.5 328.1 268.6 Net earnings 319.0 174.3 725.7 542.7 Less (earnings) loss attributable to noncontrolling interests (0.2 ) (2.8 ) 0.1 (3.4 ) Net income attributable to Laboratory Corporation of America Holdings $ 318.8 $ 171.5 $ 725.8 $ 539.3

REVENUE (Tables)

REVENUE (Tables)	9 Months Ended
	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset and Liability [Table Text Block]	September 30, 2018 December 31, 2017 Receivables, which are included in Accounts Receivable, net $ 665.7 $ 694.4 Unbilled services 322.6 318.2 Unearned revenue 286.2 377.4
Revenue from Contract with Customer [Text Block]	REVENUE Description of Revenue The Company's revenue by segment payers/customer groups for the three and nine months ended September 30, 2018 , and 2017 is as follows: For the Three Months Ended September 30, 2018 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 17 % 1 % — % — % — % — % 18 % Patients 8 % — % — % — % — % — % 8 % Medicare and Medicaid 9 % — % — % — % — % — % 9 % Third-party 25 % 2 % — % — % — % — % 27 % Total LCD revenues by payer 59 % 3 % — % — % — % — % 62 % CDD Biopharmaceutical and medical 24 % — % 3 % 4 % 2 % 5 % 38 % Total revenues 83 % 3 % 3 % 4 % 2 % 5 % 100 % For the Three Months Ended September 30, 2017 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 19 % 1 % — % — % — % — % 20 % Patients 9 % — % — % — % — % — % 9 % Medicare and Medicaid 10 % — % — % — % — % — % 10 % Third-party 27 % 2 % — % — % — % — % 29 % Total LCD revenues by payer 65 % 3 % — % — % — % — % 68 % CDD Biopharmaceutical and medical 15 % — % 3 % 4 % 3 % 7 % 32 % Total revenues 80 % 3 % 3 % 4 % 3 % 7 % 100 % For the Nine Months Ended September 30, 2018 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 17 % 1 % — % — % — % — % 18 % Patients 9 % — % — % — % — % — % 9 % Medicare and Medicaid 9 % — % — % — % — % — % 9 % Third-party 24 % 2 % — % — % — % — % 26 % Total LCD revenues by payer 59 % 3 % — % — % — % — % 62 % CDD Biopharmaceutical and medical 20 % — % 3 % 5 % 3 % 7 % 38 % Total revenues 79 % 3 % 3 % 5 % 3 % 7 % 100 % For the Nine Months Ended September 30, 2017 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 19 % 1 % — % — % — % — % 20 % Patients 9 % — % — % — % — % — % 9 % Medicare and Medicaid 10 % — % — % — % — % — % 10 % Third-party 26 % 2 % — % — % — % — % 28 % Total LCD revenues by payer 64 % 3 % — % — % — % — % 67 % CDD Biopharmaceutical and medical 15 % — % 3 % 5 % 3 % 7 % 33 % Total revenues 79 % 3 % 3 % 5 % 3 % 7 % 100 % The following is a description of the current revenue recognition policies of the Company: LCD LCD is an independent clinical laboratory business. It offers a comprehensive menu of frequently requested and specialty diagnostic tests through an integrated network of primary and specialty laboratories across the U.S. In addition to diagnostic testing, along with occupational and wellness testing for employers and forensic DNA analysis, LCD has also offered a range of other testing services, including food solutions services. Within the LCD segment, with the exception of food solutions services, a revenue transaction is initiated when LCD receives a requisition order to perform a diagnostic test. The information provided on the requisition form is used to determine the party that will be billed for the testing performed and the expected reimbursement. LCD recognizes revenue and satisfies its performance obligation for services rendered when the testing process is complete and the associated results are reported. Sales are distributed among four payer portfolios - clients, patients, Medicare and Medicaid, and third-party. LCD considers negotiated discounts and anticipated adjustments, including historical collection experience for the payer portfolio, when sales are recorded. The following are descriptions of the LCD payer portfolios: Clients Client payers represent the portion of LCD’s revenue related to physicians, hospitals, health systems, accountable care organizations (ACOs), employers and other entities where payment is received exclusively from the entity ordering the testing service. Generally, client sales are recorded on a fee-for-service basis at LCD’s client list price, less any negotiated discount. A portion of client billing is for laboratory management services, collection kits and other non-testing services or products. In these cases, revenue is recognized when services are rendered or delivered. This portfolio also includes LCD's nutritional chemistry services. LCD offers a broad range of services to the food and nutraceutical and animal feed industries. Revenue is recognized using an output-based measure of progress based on the volume of activities in each period. Patients This portfolio includes revenue from uninsured patients and member cost-share for insured patients (e.g., coinsurance, deductibles and non-covered services). Uninsured patients are billed based upon LCD’s patient fee schedules, net of any discounts negotiated with physicians on behalf of their patients. LCD bills insured patients as directed by their health plan and after consideration of the fees and terms associated with an established health plan contract. Medicare and Medicaid This portfolio relates to fee-for-service revenue from traditional Medicare and Medicaid programs. Net revenue from these programs is based on the fee schedule established by the related government authority. In addition to contractual discounts, other adjustments including anticipated payer denials are considered when determining net revenue. Any remaining adjustments to revenue are recorded at the time of final collection and settlement. These adjustments are not material to LCD’s results of operations in any period presented. Third-Party Third-party includes revenue related to MCOs. The majority of LCD's third-party revenue is reimbursed on a fee-for-service basis. These payers are billed at LCD's established list price and revenue is recorded net of contractual discounts. The majority of LCD’s MCO sales are recorded based upon contractually negotiated fee schedules with sales for non-contracted MCOs recorded based on historical reimbursement experience. In addition to contractual discounts, other adjustments including anticipated payer denials are considered when determining revenue. Any remaining adjustments to revenue are recorded at the time of final collection and settlement. These adjustments are not material to LCD’s results of operations in any period presented. Third-party reimbursement is also received through capitation agreements with MCOs and independent physician associations (IPAs). Under capitated agreements, revenue is recognized based on a negotiated per-member, per-month payment for an agreed upon menu of tests, or based upon the proportionate share earned by LCD from a capitation pool. When the agreed upon reimbursement is based solely on an established rate per member, revenue is not impacted by the volume of testing performed. Under a capitation pool arrangement, the aggregate value of an established rate per member is distributed based on the volume and complexity of the procedures performed by laboratories participating in the agreement. LCD recognizes revenue monthly, based upon the established capitation rate or anticipated distribution from a capitated pool. CDD CDD is a contract research organization (CRO) business that provides end-to-end drug development services from early-stage research to clinical trial management and beyond. CDD provides these services predominantly to biopharmaceutical and medical device companies across the world. Because the CDD client base generally consumes these drug development services across the entire portfolio of CDD pre-clinical and clinical services offerings, there is little variability in the customer base of any particular CDD service offering. The nature of CDD’s obligations include agreements to manage a full clinical trial, provide services for a specific phase of a trial, or provide research products to the customer. Generally, the amount of the transaction price estimated at the beginning of the contract is equal to the amount expected to be billed to the customer. Other payments may also factor into the calculation of transaction price, such as volume-based rebates that are retroactively applied to prior transactions in the period. Historically, a majority of CDD’s net revenues have been earned under contracts that range in duration from a few months to a few years, but can extend in duration up to five years or longer. Occasionally, CDD also has entered into minimum volume arrangements with certain customers. Under these types of arrangements, if the annual minimum dollar value of a service commitment is not reached, the customer is required to pay CDD for the shortfall. Annual minimum commitment shortfalls are not recognized until the end of the period when the amount has been determined and agreed to by the customer. CDD recognizes revenue either as services are performed or as products are delivered, depending on the nature of the work contracted. If performance is completed at a specific point in time, the Company evaluates the nature of the agreement to determine when the good or service is transferred into the customer’s control. Service contracts generally take the form of fee-for-service or fixed-price arrangements subject to pricing adjustments based on changes in scope. In cases where performance spans multiple accounting periods, revenue is recognized as services are performed, measured on a proportional-performance basis, using either input or output methods that are specific to the service provided. In an output method, revenue is determined by dividing the actual units of output achieved by the total units of output required under the contract and multiplying that percentage by the total contract value. The total contract value, or total contractual payments, represents the aggregate contracted price for each of the agreed upon services to be provided. When using an input method, revenue is recognized by dividing the actual units of input incurred by the total units of input budgeted in the contract, and multiplying that percentage by the total contract value. In each situation, the Company believes that the methods used most accurately depict the progress of the Company towards completing its obligations. Billing schedules and payment terms are generally negotiated on a contract-by-contract basis. In some cases, CDD bills the customer for the total contract value in progress-based installments as certain non-contingent billing milestones are reached over the contract duration. These milestones include, but are not limited to, contract signing, initial dosing, investigator site initiation, patient enrollment and/or database lock. The term “billing milestone” relates only to a billing trigger in a contract whereby amounts become billable and payable in accordance with a negotiated predetermined billing schedule throughout the term of a project. These billing milestones are generally not performance-based (i.e., there is no potential additional consideration tied to specific deliverables or performance). In other cases, billing and payment terms are tied to the passage of time (e.g., monthly billings). In either case, the total contract value and aggregate amounts billed to the customer would be the same at the end of the project. Proportional performance contracts typically contain a single service (e.g., management of a clinical study) and, therefore, no allocation of the contract price is required. Fee-for-service contracts are typically priced based on transaction volume. Since the volume of activities in a fee-for-service contract is unspecified, the contract price is entirely variable and is allocated to the time period in which it is earned. For contracts that include multiple distinct goods and services, CDD allocates the contract price to the goods and services based on a customer price list, if available. If a price list is not available, CDD will estimate the transaction price using either market prices or an “expected cost plus margin” approach. CDD attempts to negotiate terms that provide for billing and payment of services prior or within close proximity to the provision of services, but this is not always possible. During an ongoing project, cash payments are not necessarily representative of aggregate revenue earned at any particular point in time because revenues are recognized when services are provided while amounts billed and paid are in accordance with the negotiated billing and payment terms. In some cases, payments received are in excess of revenue recognized. For example, a contract invoicing schedule may provide for an upfront payment of 10% of the full contract value upon contract signing, but at the time of signing performance of services has not yet begun. Payments received in advance of services being provided are deferred as contract liabilities on the balance sheet. As the contracted services are subsequently performed and the associated revenue is recognized the contract liability balance is reduced by the amount of revenue recognized during the period. In other cases, services may be provided and revenue recognized before the customer is invoiced. In these cases revenue recognized will exceed amounts billed, and the difference, representing a contract asset, is recorded for the amount that is currently not billable to the customer pursuant to contractual terms. Once the customer is invoiced the contract asset is reduced for the amount billed and a corresponding account receivable is recorded. All contract assets are billable to customers within one year from the respective balance sheet date. Most contracts are terminable with or without cause by the customer, either immediately or upon notice. These contracts often require payment to CDD of expenses to wind-down the study or project, fees earned to date and, in some cases, a termination fee or a payment to CDD of some portion of the fees or profits that could have been earned by CDD under the contract if it had not been terminated early. Termination fees are included in net revenues when services are performed and realization is assured. The full range of drug development services provided by CDD are as follows: Preclinical services include the sale of research models, fee-for-service activities such as bioanalytical testing services, and proportional performance activities such as toxicology studies. Revenue for sale of research models is recognized at a point in time, typically upon shipment, when control transfers to the customer. Revenue for bioanalytical testing services is recognized upon communication of results to the customer. Revenue for proportional performance activities, including toxicology studies, is recognized using an input-based measure of progress as expenses are incurred for the research models, labor hours, and other costs attributable to the study. Through its central laboratory, CDD produces and supplies specimen collection kits that are utilized in clinical studies, and provides transportation, project management, data management, and laboratory testing services on an as-needed basis throughout the duration of its customers’ clinical studies. Revenue for central laboratory services is recognized using an output-based measure of progress based on volume of activities in each period. CDD also provides long-term specimen storage services, for which revenue is recognized using an input-based measure of progress based on costs incurred. CDD provides clinical development and commercialization services, including clinical pharmacology services, full management of Phase II through IV clinical studies, and market access solutions. Revenue for clinical pharmacology services, which includes first-in-human trials, is recognized using an output-based measure of progress based on bed nights. Revenue for full service clinical studies is recognized using an input-based measure of progress based on costs incurred (including pass-through costs such as investigator grants and reimbursable out-of-pocket expenses). Revenue for market access solutions is recognized using various methods. Revenue for fee-for-service arrangements, such as reimbursement consulting hotlines and patient assistance programs, is recognized using an output method based on transaction volume which corresponds to the amount charged to the customer. For consulting services billed based on time and materials; revenue is recognized using the right to invoice practical expedient. Contract costs The Company incurs sales commissions in the process of obtaining contracts with customers, which are recoverable through the service fees in the contract. Sales commissions that are payable upon contract award are recognized as assets and amortized over the expected contract term, along with related payroll tax expense. The amortization of commission expense is based on the weighted average contract duration for all commissionable awards in the respective business in which the commission expense is paid, which approximates the period over which goods and services are transferred to the customer. The amortization period of sales commissions ranges from approximately 12 months to 57 months, depending on the business. For businesses that enter into primarily short-term contracts, the Company applies the practical expedient which allows costs to obtain a contract to be expensed when incurred if the amortization period of the assets that would otherwise have been recognized is one year or less. Amortization of assets from sales commissions is included in selling, general, and administrative expense. The Company incurs costs to fulfill contracts with customers, which are recoverable through the service fees in the contract. Contract fulfillment costs include software implementation costs and setup costs for certain market access solutions. These costs are recognized as assets and amortized over the expected term of the contract to which the implementation relates, which is the period over which services are expected to be provided to the customer. This period typically ranges from 24-60 months. Amortization of deferred contract fulfillment costs is included in cost of goods sold. September 30, 2018 December 31, 2017 Sales commission assets $ 22.8 $ 24.0 Deferred contract fulfillment costs 12.5 1.7 Total $ 35.3 $ 25.7 Amortization related to sales commission assets and associated payroll taxes for the three-month periods ended September 30, 2018 , and 2017 , was $4.2 and $3.5 , respectively, and for the nine-month periods ended September 30, 2018 , and 2017 , was $12.8 and $10.6 , respectively. Amortization related to deferred contract fulfillment costs for the three-month periods ended September 30, 2018 , and 2017 , was $0.8 and $0.1 , respectively, and for the nine-month periods ended September 30, 2018 , and 2017 , was $3.3 and $0.3 , respectively. Impairment expense related to contract costs was immaterial to the Company’s consolidated statement of operations. The Company applies the practical expedient to not recognize the effect of financing in its contracts with customers, when the difference in timing of payment and performance is one year or less. Contract Assets and Liabilities The following table provides information about receivables, contract assets (unbilled services), and contract liabilities (unearned revenue) from contracts with customers. While CDD attempts to negotiate terms that provide for billing and payment of services prior or in close proximity to the provision of services, this is not always possible and there are fluctuations in the level of unbilled services and unearned revenue from period to period. September 30, 2018 December 31, 2017 Receivables, which are included in Accounts Receivable, net $ 665.7 $ 694.4 Unbilled services 322.6 318.2 Unearned revenue 286.2 377.4 Revenue recognized during the period, that was included in the unearned revenue balance at the beginning of the period for the nine-month period ended September 30, 2018 , was $144.8 . Bad debt expense on receivables for the nine-month period ended September 30, 2018 , was immaterial to the Company’s consolidated statement of operations. Performance Obligations Under Long-Term Contracts Long-term contracts at the Company consist primarily of fully managed clinical studies within the CDD segment. The amount of existing performance obligations under such long-term contracts unsatisfied as of September 30, 2018 , was $4,199.6 . The Company expects to recognize approximately 39% of the remaining performance obligations as revenue over the next 12 months, and the balance thereafter. The Company applied the practical expedient and does not disclose information about remaining performance obligations that have original expected durations of one year or less. The Company also did not disclose information about remaining performance obligations when the variable consideration was related to a wholly unsatisfied performance obligation within a series of obligations. Within CDD, revenue of $10.9 and $20.5 was recognized during the three and nine months ended September 30, 2018, respectively, from performance obligations that were satisfied in previous periods. This revenue comes from adjustments related to changes in scope and estimates in full service clinical studies.
Disaggregation of Revenue [Table Text Block]	The Company's revenue by segment payers/customer groups for the three and nine months ended September 30, 2018 , and 2017 is as follows: For the Three Months Ended September 30, 2018 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 17 % 1 % — % — % — % — % 18 % Patients 8 % — % — % — % — % — % 8 % Medicare and Medicaid 9 % — % — % — % — % — % 9 % Third-party 25 % 2 % — % — % — % — % 27 % Total LCD revenues by payer 59 % 3 % — % — % — % — % 62 % CDD Biopharmaceutical and medical 24 % — % 3 % 4 % 2 % 5 % 38 % Total revenues 83 % 3 % 3 % 4 % 2 % 5 % 100 % For the Three Months Ended September 30, 2017 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 19 % 1 % — % — % — % — % 20 % Patients 9 % — % — % — % — % — % 9 % Medicare and Medicaid 10 % — % — % — % — % — % 10 % Third-party 27 % 2 % — % — % — % — % 29 % Total LCD revenues by payer 65 % 3 % — % — % — % — % 68 % CDD Biopharmaceutical and medical 15 % — % 3 % 4 % 3 % 7 % 32 % Total revenues 80 % 3 % 3 % 4 % 3 % 7 % 100 % For the Nine Months Ended September 30, 2018 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 17 % 1 % — % — % — % — % 18 % Patients 9 % — % — % — % — % — % 9 % Medicare and Medicaid 9 % — % — % — % — % — % 9 % Third-party 24 % 2 % — % — % — % — % 26 % Total LCD revenues by payer 59 % 3 % — % — % — % — % 62 % CDD Biopharmaceutical and medical 20 % — % 3 % 5 % 3 % 7 % 38 % Total revenues 79 % 3 % 3 % 5 % 3 % 7 % 100 % For the Nine Months Ended September 30, 2017 U.S. Canada U.K. Switzerland Other Europe Other Total Payer/Customer LCD Clients 19 % 1 % — % — % — % — % 20 % Patients 9 % — % — % — % — % — % 9 % Medicare and Medicaid 10 % — % — % — % — % — % 10 % Third-party 26 % 2 % — % — % — % — % 28 % Total LCD revenues by payer 64 % 3 % — % — % — % — % 67 % CDD Biopharmaceutical and medical 15 % — % 3 % 5 % 3 % 7 % 33 % Total revenues 79 % 3 % 3 % 5 % 3 % 7 % 100 %
Capitalized Contract Cost [Table Text Block]	September 30, 2018 December 31, 2017 Sales commission assets $ 22.8 $ 24.0 Deferred contract fulfillment costs 12.5 1.7 Total $ 35.3 $ 25.7

BASIS OF FINANCIAL STATEMENT _3

BASIS OF FINANCIAL STATEMENT PRESENTATION (Details) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)$ / shares	Sep. 30, 2017USD ($)$ / shares	Sep. 30, 2018USD ($)$ / shares	Sep. 30, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues	$ 2,831.3	$ 2,621.4	$ 8,545.9	$ 7,563.3
Cost of Revenue	2,041.4	1,837.2	6,141.9	5,288.6
Contract with Customer, Liability	286.2		286.2			$ 377.4
Amortization of Deferred Sales Commissions	4.2	$ 3.5	12.8	10.6
Assets, Current	$ 3,274.3		3,274.3			2,733.8
Assets, Noncurrent						13,939.2
Net Cash Provided by (Used in) Operating Activities			$ 819	$ 933.1
Percent of Revenue Contributed	100.00%	100.00%	100.00%	100.00%
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification					$ 13.2
Selling, general and administrative expenses	$ 381.8	$ 381.3	$ 1,174	$ 1,081.9
Nonoperating Income (Expense)	156.2	(59.9)	35.8	(163.3)
Other Nonoperating Income		136.1		381.5
Provision for income taxes	180.6	92.5	328.1	268.6
Net earnings	319	174.3	725.7	542.7
Less: Net earnings attributable to the noncontrolling interest	(0.2)	(2.8)	0.1	(3.4)
Net Income (Loss) Attributable to Parent	$ 318.8	$ 171.5	$ 725.8	$ 539.3
Basic earnings per common share (in dollars per share) | $ / shares	$ 3.14	$ 1.68	$ 7.13	$ 5.27
Diluted earnings per common share (in dollars per share) | $ / shares	$ 3.10	$ 1.65	$ 7.04	$ 5.19
Net Cash Provided by (Used in) Investing Activities			$ 353.6	$ (2,050.4)
Net Cash Provided by (Used in) Financing Activities			(587)	1,073.5
Effect of exchange rate changes on cash and cash equivalents			(9.6)	19.3
Prior Period Reclassification Adjustment			45.1	46.5
Cash and Cash Equivalents, Period Increase (Decrease)			576	(24.5)
Assets	$ 16,661.4		16,661.4			16,673
Liabilities, Current	2,106.2		2,106.2			2,185.7
Liabilities, Noncurrent						7,662.4
Common stock, 92.8 and 93.5 shares outstanding at March 31, 2013 and December 31, 2012, respectively	20.4		20.4			20.8
Stockholders' Equity Attributable to Parent	7,248.1	$ 6,118.6	7,248.1	6,118.6	$ 5,518.2	6,804.1
Liabilities and Equity	16,661.4		16,661.4			16,673
Capitalized Contract Cost, Amortization	0.8	0.1	3.3	0.3
Deferred Revenue, Revenue Recognized			144.8
Revenue, Remaining Performance Obligation, Amount	4,199.6		4,199.6
Contract with Customer, Performance Obligation Satisfied in Previous Period	10.9		$ 20.5
Ownership percentage below which investments are generally accounted for on the cost method (in thousandths)			20.00%
LabCorp Diagnostics [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues	$ 1,752	$ 1,754.7	$ 5,336.3	$ 5,115.5
Percent of Revenue Contributed	62.00%	68.00%	62.00%	67.00%
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		$ 82.5		$ 238.7
Covance Drug Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues	$ 1,081.5	867.1	$ 3,214.1	2,448.7
Percent of Revenue Contributed	38.00%		38.00%
Investigator fees [Member] | Covance Drug Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		71		197.4
Measure of progress [Member] | Covance Drug Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		15.6		33.8
sales commissions [Member] | Covance Drug Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		2		0.8
Previous Accounting Guidance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues		2,655.2		7,645.1
Cost of Revenue		1,772.4		5,096.9
Net cash provided by (used in) operating activities, as reported				895.3
Current assets, as reported						2,682.6
Gross profit, as reported		882.8		2,548.2
Noncurrent assets, as reported						13,885.4
Total assets, as reported						16,568
Net Cash Provided by (Used in) Investing Activities, as reported				(2,050.4)
Selling, general and administrative expenses		465.3		1,320
Nonoperating Income (Expense)		136.4		382.3
Provision for income taxes		97.7		281.1
Net income (loss), including portion attributable to NCI, as reported		183.4		564.8
Less: Net earnings attributable to the noncontrolling interest		(2.8)		(3.4)
Net income (loss) attributable to Parent, as reported		$ 180.6		$ 561.4
Basic earnings per common share (in dollars per share) | $ / shares		$ 1.77		$ 5.48
Diluted earnings per common share (in dollars per share) | $ / shares		$ 1.74		$ 5.40
Net Cash Provided by (Used in) Financing Activities, as reported				$ 1,111.3
Effect of Exchange Rate on Cash and Cash Equivalents, as reported				19.4
Cash and Cash Equivalents, Period Increase (Decrease)				(24.4)
Current liabilities, as reported						2,046.1
Noncurrent liabilities, as reported						7,671.1
Noncontrolling Interest Mezzanine Equity, as reported						20.8
Shareholders Equity Attributable to Parent, as reported						6,830
Total liabilities and shareholders equity, as reported						$ 16,568
Other Current Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(51.2)
Other Noncurrent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(53.8)
Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(105)
Other Current Liabilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(139.6)
Other Noncurrent Liabilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(8.7)
Noncontrolling Interest [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				0
Shareholders' Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(25.9)
Total liabilities and shareholder's equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				(105)
Revenue from Contract with Customer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		$ (33.8)		(81.8)
ASU 715 pension adjustment to previously reported amounts		0		0
Gross profit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(98.4)		(273.1)
ASU 715 pension adjustment to previously reported amounts		(0.2)		(0.4)
Selling, General and Administrative Expenses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(84.5)		(239.4)
ASU 715 pension adjustment to previously reported amounts		(0.5)		(1.3)
Nonoperating Income (Expense) [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(0.4)		(0.9)
ASU 715 pension adjustment to previously reported amounts		(0.7)		(1.7)
Provision for income taxes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(5.2)		(12.5)
ASU 715 pension adjustment to previously reported amounts		0		0
Net earnings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(9.1)		(22.1)
ASU 715 pension adjustment to previously reported amounts		0		0
Net earnings attributable to NCI [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		0		0
ASU 715 pension adjustment to previously reported amounts		0		0
Cost of Sales [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(64.6)		(191.3)
ASU 715 pension adjustment to previously reported amounts		(0.2)		(0.4)
Net earnings attributable to company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts		(9.1)		(22.1)
ASU 715 pension adjustment to previously reported amounts		$ 0		0
Net cash from operating activities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				$ 0
ASC 230 Cash flow presentation adjustment				(8,700,000)
Prior Period Reclassification Adjustment				$ 46.5
Net cash from investing activities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				0
Net Cash Provided by (Used in) Investing Activities				0
Prior Period Reclassification Adjustment				0
Net cash from financing activities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				0
Net Cash Provided by (Used in) Financing Activities				8.7
Prior Period Reclassification Adjustment				(46.5)
Effect of exchange rate on cash and cash equivalents [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
ASU 606 adjustment to previously reported amounts				0.1
Effect of exchange rate changes on cash and cash equivalents				0
Prior Period Reclassification Adjustment				$ 0

EARNINGS PER SHARE (Reconciliat

EARNINGS PER SHARE (Reconciliation of Basic Earnings Per Share to Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income [Abstract]
Net earnings attributable to Laboratory Corporation of America Holdings	$ 318.8	$ 171.5	$ 725.8	$ 539.3
Shares [Abstract]
Net earnings, basic (in shares)	101.6	102.2	101.8	102.4
Dilutive effect of employee stock options and awards, (in shares)	1	1.4	1.2	1.4
Effect of convertible debt, net of tax, (in shares)	0.1	0.1	0.1	0.1
Per Share Amount [Abstract]
Basic earnings per common share (in dollars per share)	$ 3.14	$ 1.68	$ 7.13	$ 5.27
Diluted earnings per common share (in dollars per share)	$ 3.10	$ 1.65	$ 7.04	$ 5.19
Net Income (Loss) Available to Common Stockholders, Diluted	$ 318.8	$ 171.5	$ 725.8	$ 539.3
Weighted Average Number of Shares Outstanding, Diluted	102.7	103.7	103.1	103.9

EARNINGS PER SHARE (Potential c

EARNINGS PER SHARE (Potential common shares not included in computation of diluted earnings per share) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Stock options (in shares)	0.1	0.1	0.1	0.1

RESTRUCTURING AND OTHER SPECI_3

RESTRUCTURING AND OTHER SPECIAL CHARGES (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Goodwill, Acquired During Period	$ 49.5		$ 1,009.8
Restructuring Reserve	48.1		54.7
Restructuring Charges	38.8
Restructuring Reserve Settled With Cash And Other Adjustment	(43.1)
Net restructuring charges	36.5	$ 64.6
Restructuring charges related to severance and other employee costs	30	27.2
Restructuring charges related to contractual obligations associated with leased facilities and other facility related costs	8.8	18
Employee Severance Benefits Related Restructuring Reserve Accrual Adjustment	1.1	1.4
Asset Impairment Charges	5.3	23.5
Unused facility restructuring reserves	1.2	0.1
Reduction in total prior restructuring accruals	(2.3)
Restructuring Reserve, Current	22.6
Restructuring Reserve, Noncurrent	25.5
special charge - consulting expense	4.3	8
Business Combination, Acquisition Related Costs		29.8
Special charge, accelerated equity compensation		0.9
Special charge, accelerated equity compensation	43.1
Special charge, malware attack	12.6
Special charge - one-time tax liability	31.1
Covance Drug Development [Member]
Restructuring Cost and Reserve [Line Items]
Goodwill, Acquired During Period	45.6		811.3
Net restructuring charges	23.3	50.6
Asset Impairment Charges	5.3	20.9
Covance Drug Development [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	10.1		8.3
Restructuring Charges	19.3
Restructuring Reserve Settled With Cash And Other Adjustment	(16.3)
Reduction in total prior restructuring accruals	1.2
Covance Drug Development [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	29.4		34.6
Restructuring Charges	5.8
Restructuring Reserve Settled With Cash And Other Adjustment	(10.4)
Reduction in total prior restructuring accruals	0.6
LabCorp Diagnostics [Member]
Restructuring Cost and Reserve [Line Items]
Goodwill, Acquired During Period	3.9		198.5
Net restructuring charges	13.2	14
LabCorp Diagnostics [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	1.3		1.7
Restructuring Charges	10.7
Restructuring Reserve Settled With Cash And Other Adjustment	(11.1)
Reduction in total prior restructuring accruals	0
LabCorp Diagnostics [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	7.3		$ 10.1
Restructuring Charges	3
Restructuring Reserve Settled With Cash And Other Adjustment	(5.3)
Reduction in total prior restructuring accruals	(0.5)
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Other Special Charges	$ 7.3	$ 8.2

RESTRUCTURING RESERVES (Details

RESTRUCTURING RESERVES (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Unused facility restructuring reserves	$ 1.2	$ 0.1
special charge - consulting expense	4.3	8
Special charge, accelerated equity compensation		0.9
Balance, beginning of period	54.7
Restructuring charges	38.8
Reduction of prior restructuring accruals	(2.3)
Cash payments and other adjustments	(43.1)
Balance, end of period	48.1
Current			$ 22.6
Non-current			25.5
Total Restructuring Reserve	54.7		48.1
Employee Severance Benefits Related Restructuring Reserve Accrual Adjustment	1.1	$ 1.4
LabCorp Diagnostics [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	1.7
Restructuring charges	10.7
Reduction of prior restructuring accruals	0
Cash payments and other adjustments	(11.1)
Balance, end of period	1.3
Total Restructuring Reserve	1.7		1.3
LabCorp Diagnostics [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	10.1
Restructuring charges	3
Reduction of prior restructuring accruals	(0.5)
Cash payments and other adjustments	(5.3)
Balance, end of period	7.3
Total Restructuring Reserve	10.1		7.3
Covance Drug Development [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	8.3
Restructuring charges	19.3
Reduction of prior restructuring accruals	1.2
Cash payments and other adjustments	(16.3)
Balance, end of period	10.1
Total Restructuring Reserve	8.3		10.1
Covance Drug Development [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	34.6
Restructuring charges	5.8
Reduction of prior restructuring accruals	0.6
Cash payments and other adjustments	(10.4)
Balance, end of period	29.4
Total Restructuring Reserve	$ 34.6		$ 29.4

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Goodwill [Line Items]
Severance Costs	$ 30	$ 27.2
Intangible Assets, Gross (Excluding Goodwill)	5,545.2		$ 5,566.2
Balance as of January 1	7,400.9
Goodwill, Acquired During Period	49.5		1,009.8
Goodwill, Other Increase (Decrease)	0		170.5
Goodwill, Written off Related to Sale of Business Unit	(24.1)		0
Adjustments to goodwill	(63.6)		137.2
Balance at end of period	7,362.7		7,400.9
Finite-Lived Intangible Assets, Accumulated Amortization	1,554.3		1,400.1
Intangible Assets, Net (Excluding Goodwill)	3,990.9		4,166.1
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Balance as of January 1	3,673.9
Goodwill, Acquired During Period	3.9		198.5
Goodwill, Other Increase (Decrease)	0		170.5
Goodwill, Written off Related to Sale of Business Unit	(24.1)		0
Adjustments to goodwill	(4.2)		1.1
Balance at end of period	3,649.5		3,673.9
Covance Drug Development [Member]
Goodwill [Line Items]
Balance as of January 1	3,727
Goodwill, Acquired During Period	45.6		811.3
Goodwill, Other Increase (Decrease)	0		0
Goodwill, Written off Related to Sale of Business Unit	0		0
Adjustments to goodwill	(59.4)		136.1
Balance at end of period	3,713.2		3,727
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	4,115.7		4,118.1
Finite-Lived Intangible Assets, Accumulated Amortization	1,106.5		992.8
Intangible Assets, Net (Excluding Goodwill)	3,009.2		3,125.3
Patents, Licenses And Technology [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	454.6		457.9
Finite-Lived Intangible Assets, Accumulated Amortization	207.8		188.6
Intangible Assets, Net (Excluding Goodwill)	246.8		269.3
Noncompete Agreements [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	75.8		75.8
Finite-Lived Intangible Assets, Accumulated Amortization	53		48.3
Intangible Assets, Net (Excluding Goodwill)	22.8		27.5
Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	405		407.9
Finite-Lived Intangible Assets, Accumulated Amortization	183.3		167.9
Intangible Assets, Net (Excluding Goodwill)	221.7		240
Use Rights [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.8		10.8
Finite-Lived Intangible Assets, Accumulated Amortization	3.7		2.5
Intangible Assets, Net (Excluding Goodwill)	7.1		8.3
Canadian licenses [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	483.3		495.7
Finite-Lived Intangible Assets, Accumulated Amortization	0		0
Intangible Assets, Net (Excluding Goodwill)	$ 483.3		$ 495.7

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS (Components of identifiable intangible assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 5,545.2	$ 5,566.2
Accumulated Amortization	(1,554.3)	(1,400.1)
Intangible Assets, Net (Excluding Goodwill)	3,990.9	4,166.1
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	4,115.7	4,118.1
Accumulated Amortization	(1,106.5)	(992.8)
Intangible Assets, Net (Excluding Goodwill)	3,009.2	3,125.3
Patents, Licenses And Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	454.6	457.9
Accumulated Amortization	(207.8)	(188.6)
Intangible Assets, Net (Excluding Goodwill)	246.8	269.3
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	75.8	75.8
Accumulated Amortization	(53)	(48.3)
Intangible Assets, Net (Excluding Goodwill)	22.8	27.5
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	405	407.9
Accumulated Amortization	(183.3)	(167.9)
Intangible Assets, Net (Excluding Goodwill)	221.7	240
Use Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.8	10.8
Accumulated Amortization	(3.7)	(2.5)
Intangible Assets, Net (Excluding Goodwill)	7.1	8.3
Canadian licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	483.3	495.7
Accumulated Amortization	0	0
Intangible Assets, Net (Excluding Goodwill)	$ 483.3	$ 495.7

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 7,362.7		$ 7,362.7		$ 7,400.9	$ 6,424.4
Amortization of intangible assets	54.7	$ 54.6	175.5	$ 153.6
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012	51.3		51.3
Estimated amortization expense, 2013	222.5		222.5
Estimated amortization expense, 2014	214.4		214.4
Estimated amortization expense, 2015	208.1		208.1
Estimated amortization expense, 2016	202.5		202.5
Estimated amortization expense, Thereafter	2,522.8		2,522.8
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,649.5		3,649.5		3,673.9	3,644.8
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 3,713.2		$ 3,713.2		$ 3,727	$ 2,779.6

DEBT (Short-term borrowings and

DEBT (Short-term borrowings and current portion of long-term debt) (Table) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Capital Lease Obligations, Current	$ 8	$ 8.3
Total short-term borrowings and current portion of long-term debt	$ 417.8	417.5
Short-term borrowings and current portion of long-term debt	Short-term borrowings and the current portion of long-term debt at September 30, 2018 , and December 31, 2017 , consisted of the following: September 30, December 31, 2017 Zero-coupon convertible subordinated notes $ 8.6 $ 8.8 2.50% senior notes due 2018 400.0 400.0 Debt issuance costs (0.6 ) (1.4 ) Current portion of capital leases 8.0 8.3 Current portion of note payable 1.8 1.8 Total short-term borrowings and current portion of long-term debt $ 417.8 $ 417.5
Senior notes due 2020 [Member]
Short-term Debt [Line Items]
Senior Notes, Noncurrent	$ 500	500
Debt Instrument, Interest Rate, Stated Percentage	4.625%
Senior notes due 2022 [Member]
Short-term Debt [Line Items]
Senior Notes, Noncurrent	$ 500	$ 500

DEBT (Long-term debt) (Details)

DEBT (Long-term debt) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 19, 2014USD ($)
Debt Instrument [Line Items]
Long-term Debt [Text Block]		Long-term debt at September 30, 2018 , and December 31, 2017 , consisted of the following: September 30, December 31, 2017 2.625% senior notes due 2020 $ 500.0 $ 500.0 4.625% senior notes due 2020 599.5 604.1 3.20% senior notes due 2022 500.0 500.0 3.75% senior notes due 2022 500.0 500.0 4.00% senior notes due 2023 300.0 300.0 3.25% senior notes due 2024 600.0 600.0 3.60% senior notes due 2025 1,000.0 1,000.0 3.60% senior notes due 2027 600.0 600.0 4.70% senior notes due 2045 900.0 900.0 2014 Term loan — 72.0 2017 Term loan 527.0 750.0 Debt issuance costs (42.0 ) (48.2 ) Capital leases 52.6 57.8 Note payable 7.5 8.9 Total long-term debt $ 6,044.6 $ 6,344.6
Long-term Debt, Excluding Current Maturities	$ 6,044.6	$ 6,044.6	$ 6,344.6
Line of Credit Facility, Fair Value of Amount Outstanding	0	0	72
Other Long-term Debt	0	0	57.8
Capital Lease Obligations, Noncurrent	52.6	52.6
Line of Credit Facility, Maximum Borrowing Capacity				$ 1,000
Credit Facility Option to Increase				350
Credit Facility, Maximum Swing Line Borrowings				100
Capital lease obligation	8	8	8.3
Senior notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	599.5	599.5	604.1
Senior Notes, Noncurrent	$ 500	$ 500	500
Stated interest rate percentage	4.625%	4.625%
Senior notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 500	$ 500	500
Senior Notes, Noncurrent	500	500	500
Senior notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	300	300	300
Senior notes due 2025 [Member] [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	1,000	1,000	1,000
Senior notes due 2045 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 900	$ 900	$ 900
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt to EBITDA (Leverage) Ratio	0	0
Credit Facility, Maximum Letters of Credit				$ 150
Prime Rate [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate Description	0.00% to 0.25%
Prime Rate [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate Description	0.125% to 1.00%
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Commitment Fee Description	0.10% to 0.25%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate Description	0.775% to 1.25%
London Interbank Offered Rate (LIBOR) [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate Description	1.125% to 2.00%

DEBT (Senior Notes) (Details)

DEBT (Senior Notes) (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Dec. 19, 2014
Debt Instrument [Line Items]
Senior notes due 2018	$ 400	$ 400
Convertible Subordinated Debt, Current	8.6	8.8
Short term debt issuance costs	0.6	1.4
Long-term Debt, Excluding Current Maturities	6,044.6	6,344.6
Long-term Line of Credit	0
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,000
Credit Facility Option to Increase			350
Credit Facility, Maximum Swing Line Borrowings			$ 100
Fair Value Hedges, Net	$ 0.5
Debt Instrument, Basis Spread on Variable Rate	2.298%
Line of Credit Facility, Fair Value of Amount Outstanding	$ 0	72
Long term debt issuance costs	42	48.2
Capital Lease Obligations, Noncurrent	52.6
Other Long-term Debt	0	57.8
Capital Lease Obligations, Current	8	8.3
Notes Payable	1.8	1.8
Debt, Current	417.8	417.5
Foreign Currency Contract, Asset, Fair Value Disclosure	8.1
Senior notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	300	300
Senior notes due 2024 [Member] [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 600	600
Debt Instrument, Interest Rate, Effective Percentage	3.25%
Senior notes due 2025 [Member] [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount	$ 300
Senior notes due 2027 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 600	600
Debt Instrument, Interest Rate, Effective Percentage	3.60%
Senior notes due 2024 and 2027 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 1,200
Net Proceeds from Debt	$ 1,190.1
Senior notes due 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	2.20%
Senior notes due 2045 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 900	900
Cross currency swap maturing 2022 [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount	300
Senior notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	599.5	604.1
Senior Notes, Noncurrent	$ 500	500
Stated interest rate percentage	4.625%
2017 Term Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	$ 527	$ 750

DEBT (Convertible Subordinated

DEBT (Convertible Subordinated Notes) (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)shares	Sep. 30, 2018USD ($)shares	Sep. 30, 2017USD ($)
Zero Coupon Convertible Subordinated Notes [Line Items]
Number of trading days used to establish contingent cash interest rate on zero-coupon subordinated notes (in days)	five
Principal Amount At Maturity Of Zero Coupon Subordinated Notes Converted		$ 300,000
Value Of Cash And Common Stock In Connection With Conversions Of Zero Coupon Subordinated Notes Settled In Current Period		700,000
Payments On Zero Coupon Subordinated Notes		$ 300,000	$ 25,100,000
Stock Issued During Period, Shares, Conversion of Convertible Securities | shares		0
tax benefit realized upon conversion of zero coupon convertible debt		$ 200,000
Zero-coupon convertible subordinated notes [Member]
Zero Coupon Convertible Subordinated Notes [Line Items]
Minimum contingent cash interest rate on zero-coupon subordinated notes (in hundredths)	0.125%
Stock conversion rate for zero-coupon subordinated notes (per thousand) | shares	13.4108	13.4108
Principal amount of zero-coupon subordinated notes	$ 1,000,000,000	$ 1,000,000,000

DEBT (Credit Facilities) (Detai

DEBT (Credit Facilities) (Details) $ in Millions	3 Months Ended
	Sep. 30, 2018USD ($)Rate	Dec. 31, 2017USD ($)	Dec. 19, 2014USD ($)
Line of Credit Facility [Line Items]
Long-term Debt, Excluding Current Maturities	$ 6,044.6	$ 6,344.6
Convertible Subordinated Debt, Current	8.6	8.8
Long-term Line of Credit	0
Line of Credit Facility, Fair Value of Amount Outstanding	0	72
Revolving Credit Facility, maximum borrowing capacity			$ 1,000
Capital Lease Obligations, Current	8	8.3
Notes Payable	1.8	1.8
Debt, Current	417.8	417.5
Other Long-term Debt	0	57.8
Credit Facility Option to Increase			350
Credit Facility, Maximum Swing Line Borrowings			100
Notes Payable	$ 7.5	8.9
2017 Term Loan [Member]
Line of Credit Facility [Line Items]
Revolving Credit Facility, interest rate at period end	3.37%
Senior notes due 2027 [Member]
Line of Credit Facility [Line Items]
Long-term Debt, Excluding Current Maturities	$ 600	600
Revolving Credit Facility, interest rate at period end | Rate	3.60%
Senior notes due 2024 [Member] [Member]
Line of Credit Facility [Line Items]
Long-term Debt, Excluding Current Maturities	$ 600	600
Revolving Credit Facility, interest rate at period end | Rate	3.25%
Senior notes due 2020 [Member]
Line of Credit Facility [Line Items]
Senior Notes, Noncurrent	$ 500	500
Long-term Debt, Excluding Current Maturities	$ 599.5	604.1
Debt Instrument, Interest Rate, Stated Percentage	4.625%
Senior notes due 2045 [Member]
Line of Credit Facility [Line Items]
Long-term Debt, Excluding Current Maturities	$ 900	900
Senior notes due 2022 [Member]
Line of Credit Facility [Line Items]
Senior Notes, Noncurrent	500	500
Long-term Debt, Excluding Current Maturities	500	500
2017 Term Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	$ 527	$ 750
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit Facility, Maximum Letters of Credit			$ 150
Debt to EBITDA (leverage) ratio	0
Prime Rate [Member] | Term Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	0.125% to 1.00%
Prime Rate [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	0.00% to 0.25%
Prime Rate [Member] | 2017 Term Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	0.0% to 0.50%
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Description	0.10% to 0.25%
London Interbank Offered Rate (LIBOR) [Member] | Term Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	1.125% to 2.00%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	0.775% to 1.25%
London Interbank Offered Rate (LIBOR) [Member] | 2017 Term Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate Description	0.875% to 1.50%

PREFERRED STOCK AND COMMON SH_2

PREFERRED STOCK AND COMMON SHAREHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 843.5
Rollforward of common shares issued
Commons Stock Issued During Period Shares Employee Stock Plans		1.5
Stock Repurchased and Retired During Period, Shares		1.7
Stock Repurchased During Period, Shares	1.7
Rollforward of Share Repurchase Program
Outstanding common stock repurchase authorization, beginning balance		$ 401.4
Purchase of common stock		(300)	$ (298.1)
Outstanding common stock repurchase authorization, ending balance	$ 1,000	$ 1,000
Common Shares Outstanding Rollforward [Abstract]
Common shares outstanding, beginning balance (in shares)		101.9
Commons Stock Issued During Period Shares Employee Stock Plans		1.5
Stock Repurchased and Retired During Period, Shares		1.7
Common shares outstanding, ending balance (in shares)	101.4	101.4
Commons Stock Issued During Period Shares Employee Stock Plans		1.5
Rollforward of common shares held in treasury
Treasury Stock, Carrying Basis				$ 300
Common Stock, Shares Authorized				265
Common Stock, Par or Stated Value Per Share				$ 0.10
Preferred Stock, Shares Authorized				30
Preferred Stock, Par or Stated Value Per Share				$ 0.10
Stock Repurchased and Retired During Period, Shares		1.7
Preferred Stock, Shares Outstanding				0
Restricted Stock Awards And Performance Shares Surrendered, share amount		0.3
Common Stock [Member]
Rollforward of common shares issued
Common shares issued, beginning balance (in shares)		125.1
Commons Stock Issued During Period Shares Employee Stock Plans		1.5
Stock Repurchased and Retired During Period, Shares		1.7
Common shares issued, ending balance (in shares)	124.9	124.9
Common Stock, Shares, Issued	124.9	125.1		124.9
Common Shares Outstanding Rollforward [Abstract]
Commons Stock Issued During Period Shares Employee Stock Plans		1.5
Stock Repurchased and Retired During Period, Shares		1.7
Commons Stock Issued During Period Shares Employee Stock Plans		1.5
Rollforward of common shares held in treasury
Stock Repurchased and Retired During Period, Shares		1.7
Restricted Stock Awards And Performance Shares Surrendered, share amount		0
Treasury Stock, Common [Member]
Rollforward of common shares issued
Commons Stock Issued During Period Shares Employee Stock Plans		0
Stock Repurchased and Retired During Period, Shares		0
Common Shares Outstanding Rollforward [Abstract]
Commons Stock Issued During Period Shares Employee Stock Plans		0
Stock Repurchased and Retired During Period, Shares		0
Commons Stock Issued During Period Shares Employee Stock Plans		0
Rollforward of common shares held in treasury
Common shares held in Treasury, beginning balance (in shares)		(23.2)
Common shares held in Treasury, ending balance (in shares)	(23.5)	(23.5)
Treasury Stock, Shares	23.5	23.2		23.5
Stock Repurchased and Retired During Period, Shares		0
Restricted Stock Awards And Performance Shares Surrendered, share amount		0.3

PREFERRED STOCK AND COMMON SH_3

PREFERRED STOCK AND COMMON SHAREHOLDERS' EQUITY PREFERRED STOCK AND COMMON SHAREHOLDERS' EQUITY - Accumulated Other Comprehensive Earnings (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]			The components of accumulated other comprehensive earnings are as follows: Foreign Currency Translation Adjustments Net Benefit Plan Adjustments Accumulated Other Comprehensive Earnings (Loss) Balance at December 31, 2017 $ (240.7 ) $ (93.0 ) $ (333.7 ) Other comprehensive earnings (loss) before reclassifications (82.2 ) 9.1 (73.1 ) Tax effect of adjustments 2.5 (3.5 ) (1.0 ) Balance at September 30, 2018 $ (320.4 ) $ (87.4 ) $ (407.8 )
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax			$ 9.1
Other Comprehensive Income (Loss), before Reclassifications, before Tax			(73.1)
Accumulated Other Comprehensive Earnings [Roll Forward]
Foreign Currency Translation Adjustments, Beginning balance			(240.7)
Other comprehensive income before reclassifications			(82.2)
Tax effect of adjustments			2.5
Foreign Currency Translation Adjustments, Ending balance	$ (320.4)		(320.4)
Net Benefit Plan Adjustments, Beginning balance			(93)
Tax effect of adjustments			(3.5)
Net Benefit Plan Adjustments, Ending balance	(87.4)		(87.4)
Accumulated Other Comprehensive Earnings, Beginning balance			(333.7)
Other comprehensive income before reclassifications			(82.2)
Tax effect of adjustments	(4)	$ (20.2)	(1)	$ (41)
Accumulated Other Comprehensive Earnings, Ending balance	$ (407.8)		$ (407.8)

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Gross unrecognized income tax benefits	$ 18.8	$ 18.8	$ 19.5
Accrued interest and penalties related to unrecognized income tax benefits	8.6	8.6	7.9
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 28.1	$ 44.1	$ 519

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Sep. 30, 2018USD ($)	Aug. 24, 2012Recipients$ / Violation
Loss Contingencies [Line Items]
Number of Recipients | Recipients		39
Proposed damages per violation | $ / Violation		0.0005
Amount Outstanding Letters Of Credit | $	$ 72.2

PENSION AND POSTRETIREMENT PL_2

PENSION AND POSTRETIREMENT PLANS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosures [Line Items]
Payment for Pension Benefits	$ 25.3		$ 27.1
Minimum non-elective contribution (NEC) % for the 401(K) plan (in hundredths)	3.00%
Discretionary Contribution Percentage Mininum	1.00%
Discretionary Contribution Percentage Maximum	3.00%
Defined contribution retirement plan cost	$ 17.3	$ 14.9	$ 49.1	$ 43.6
Defined Benefit Plan and Postretirement Plan Disclosure
Schedule of Pensions and Postretirement Plans			As a result of the Covance acquisition, the Company sponsors two defined benefit pension plans for the benefit of its employees at two U.K. subsidiaries and one defined benefit pension plan for the benefit of its employees at a German subsidiary, all of which are legacy plans of previously acquired companies. Benefit amounts for all three plans are based upon years of service and compensation. The German plan is unfunded while the U.K. pension plans are funded. The Company’s funding policy has been to contribute annually amounts at least equal to the local statutory funding requirements. U.K. Plans Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 0.9 $ 1.0 $ 2.7 $ 2.8 Interest cost on benefit obligation 1.8 1.9 5.7 5.6 Expected return on plan assets (3.1 ) (2.9 ) (9.7 ) (8.5 ) Net (gain) from prior periods — 0.2 — 0.5 Defined benefit plan costs $ (0.4 ) $ 0.2 $ (1.3 ) $ 0.4 Assumptions used to determine defined benefit plan cost Discount rate 2.5 % 2.7 % 2.5 % 2.7 % Expected return on assets 4.5 % 4.7 % 4.5 % 4.7 % Salary increases 3.6 % 3.8 % 3.6 % 3.8 % German Plan Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 0.3 $ 0.3 $ 0.9 $ 0.8 Interest cost on benefit obligation 0.1 0.1 0.5 0.4 Defined benefit plan costs $ 0.4 $ 0.4 $ 1.4 $ 1.2 Assumptions used to determine defined benefit plan cost Discount rate 1.7 % 1.7 % 1.7 % 1.7 % Expected return on assets N/A N/A N/A N/A Salary increases 2.0 % 2.0 % 2.0 % 2.0 % The effect on operations for the Company Plan and the PEP is summarized as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 1.3 $ 1.4 $ 3.9 $ 4.2 Interest cost on benefit obligation 3.3 3.6 9.8 10.8 Expected return on plan assets (4.1 ) (4.1 ) (12.3 ) (12.3 ) Net amortization and deferral 2.9 2.8 8.8 8.3 Defined benefit plan costs $ 3.4 $ 3.7 $ 10.2 $ 11.0
Pension And Postretirement Plans			PENSION AND POST-RETIREMENT PLANS The Company’s defined contribution retirement plan (401K Plan) covers substantially all legacy LabCorp employees. All employees eligible for the 401K Plan receive a minimum 3% non-elective contribution concurrent with each payroll period. The 401K Plan also permits discretionary contributions by the Company of up to 1% and up to 3% of pay for eligible employees based on years of service with the Company. The cost of this plan was $17.3 and $14.9 for the three months ended September 30, 2018 , and 2017 , respectively, and was $49.1 and $43.6 during the nine months ended September 30, 2018 , and 2017 , respectively. As a result of the Covance acquisition, the Company also incurred expense of $16.3 and $14.0 for the Covance 401K plan during the three months ended September 30, 2018 , and 2017 , respectively, and $51.6 and $42.6 during the nine months ended September 30, 2018 , and 2017 , respectively. All of the Covance U.S. employees, excluding legacy Chiltern employees, are eligible to participate in the Covance 401K plan, which features a maximum 4.5% Company match, based upon a percentage of the employee’s contributions. Chiltern employees are eligible to participate in the Chiltern 401K plan, which features a maximum 3.0% Company match, based upon a percentage of the employee's contributions. The Company also maintains a frozen defined benefit retirement plan (Company Plan), which as of December 31, 2009, covered substantially all employees. The benefits to be paid under the Company Plan are based on years of credited service through December 31, 2009, and ongoing interest credits. Effective January 1, 2010, the Company Plan was closed to new participants. The Company’s policy is to fund the Company Plan with at least the minimum amount required by applicable regulations. The Company maintains a second, unfunded, non-contributory, non-qualified defined benefit retirement plan (PEP), which as of December 31, 2009, covered substantially all of its senior management group. The PEP supplements the Company Plan and was closed to new participants effective January 1, 2010. The effect on operations for the Company Plan and the PEP is summarized as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 1.3 $ 1.4 $ 3.9 $ 4.2 Interest cost on benefit obligation 3.3 3.6 9.8 10.8 Expected return on plan assets (4.1 ) (4.1 ) (12.3 ) (12.3 ) Net amortization and deferral 2.9 2.8 8.8 8.3 Defined benefit plan costs $ 3.4 $ 3.7 $ 10.2 $ 11.0 During the three and nine months ended September 30, 2018 , the Company contributed $25.3 and $27.1 , respectively, to the Company Plan. As a result of the Covance acquisition, the Company also has a frozen non-qualified Supplemental Executive Retirement Plan (SERP). The SERP, which is not funded, is intended to provide retirement benefits for certain executive officers of the Company who were formerly employees of Covance. Benefit amounts are based upon years of service and compensation of the participating employees. The components of the net periodic pension cost for the three and nine months ended September 30, 2018 , and 2017, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest cost $ 0.1 $ 0.1 $ 0.1 $ 0.2 Settlement gain — (0.1 ) — (0.3 ) Net periodic pension cost $ 0.1 $ — $ 0.1 $ (0.1 ) The Company has assumed the obligations under a subsidiary’s post-retirement medical plan. Coverage under this plan is restricted to a limited number of employees/retirees of the subsidiary. The Company funds the plan through monthly contributions to a Health Reimbursement Arrangement, which can be used by eligible participants to purchase health care insurance through insurance exchanges. Effective January 1, 2017, Health Reimbursement Arrangement contributions for Medicare eligible participants ceased. The effect on operations of the post-retirement medical plan is shown in the following table: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest cost on benefit obligation $ 0.1 $ 0.1 0.2 0.3 Net amortization and deferral (0.4 ) (1.7 ) (1.0 ) (5.1 ) Post-retirement medical plan benefits $ (0.3 ) $ (1.6 ) $ (0.8 ) $ (4.8 ) Also as a result of the Covance acquisition, the Company sponsors a post-employment retiree health and welfare plan for the benefit of eligible retirees at certain U.S. subsidiaries who retire after satisfying service and age requirements. Effective January 1, 2017, this plan ceased directly providing medical, prescription drug and dental coverage options previously available to eligible participants. Instead, the Company will fund the plan through monthly contributions to a Health Reimbursement Arrangement, which can be used by non-Medicare eligible participants to purchase health care insurance through insurance exchanges. The net periodic post-retirement benefit cost for the three months ended September 30, 2018 , and 2017 , was $(0.1) and $0.5 , respectively, and was $(0.3) and $1.5 for the nine months ended September 30, 2018 , and 2017 , respectively. As a result of the Covance acquisition, the Company sponsors two defined benefit pension plans for the benefit of its employees at two U.K. subsidiaries and one defined benefit pension plan for the benefit of its employees at a German subsidiary, all of which are legacy plans of previously acquired companies. Benefit amounts for all three plans are based upon years of service and compensation. The German plan is unfunded while the U.K. pension plans are funded. The Company’s funding policy has been to contribute annually amounts at least equal to the local statutory funding requirements. U.K. Plans Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 0.9 $ 1.0 $ 2.7 $ 2.8 Interest cost on benefit obligation 1.8 1.9 5.7 5.6 Expected return on plan assets (3.1 ) (2.9 ) (9.7 ) (8.5 ) Net (gain) from prior periods — 0.2 — 0.5 Defined benefit plan costs $ (0.4 ) $ 0.2 $ (1.3 ) $ 0.4 Assumptions used to determine defined benefit plan cost Discount rate 2.5 % 2.7 % 2.5 % 2.7 % Expected return on assets 4.5 % 4.7 % 4.5 % 4.7 % Salary increases 3.6 % 3.8 % 3.6 % 3.8 % German Plan Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost for administrative expenses $ 0.3 $ 0.3 $ 0.9 $ 0.8 Interest cost on benefit obligation 0.1 0.1 0.5 0.4 Defined benefit plan costs $ 0.4 $ 0.4 $ 1.4 $ 1.2 Assumptions used to determine defined benefit plan cost Discount rate 1.7 % 1.7 % 1.7 % 1.7 % Expected return on assets N/A N/A N/A N/A Salary increases 2.0 % 2.0 % 2.0 % 2.0 %
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	0	(0.1)	$ 0	(0.3)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan and Postretirement Plan Disclosure
Interest cost on benefit obligation	0.1	0.1	0.2	0.3
Net amortization and deferral	(0.4)	(1.7)	(1)	(5.1)
Defined benefit/postretirement plan costs	(0.3)	(1.6)	(0.8)	(4.8)
Pension Plan [Member]
Defined Benefit Plan and Postretirement Plan Disclosure
Service cost for benefits earned	1.3	1.4	3.9	4.2
Interest cost on benefit obligation	3.3	3.6	9.8	10.8
Expected return on plan assets	(4.1)	(4.1)	(12.3)	(12.3)
Net amortization and deferral	2.9	2.8	8.8	8.3
Defined benefit/postretirement plan costs	3.4	3.7	$ 10.2	11
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan and Postretirement Plan Disclosure
Schedule of Costs of Retirement Plans [Table Text Block]			The components of the net periodic pension cost for the three and nine months ended September 30, 2018 , and 2017, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest cost $ 0.1 $ 0.1 $ 0.1 $ 0.2 Settlement gain — (0.1 ) — (0.3 ) Net periodic pension cost $ 0.1 $ — $ 0.1 $ (0.1 )
Interest cost on benefit obligation	0.1	0.1	$ 0.1	0.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	0.1	0	$ 0.1	(0.1)
Postretirement Health Coverage [Member]
Defined Benefit Plan and Postretirement Plan Disclosure
Schedule of Costs of Retirement Plans [Table Text Block]			The effect on operations of the post-retirement medical plan is shown in the following table: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Interest cost on benefit obligation $ 0.1 $ 0.1 0.2 0.3 Net amortization and deferral (0.4 ) (1.7 ) (1.0 ) (5.1 ) Post-retirement medical plan benefits $ (0.3 ) $ (1.6 ) $ (0.8 ) $ (4.8 )
Defined benefit/postretirement plan costs	(0.1)	0.5	$ (0.3)	1.5
Other Pension, Postretirement and Supplemental Plans [Member]
Defined Benefit Plan and Postretirement Plan Disclosure
Service cost for benefits earned	0.9	1	2.7	2.8
Interest cost on benefit obligation	1.8	1.9	5.7	5.6
Expected return on plan assets	(3.1)	(2.9)	(9.7)	(8.5)
Net amortization and deferral	0	0.2	0	0.5
Defined benefit/postretirement plan costs	$ (0.4)	$ 0.2	$ (1.3)	$ 0.4
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	2.50%	2.70%	2.50%	2.70%
Defined Benefit Plan Expected Rate Of Return On Assets Other Assets	4.50%	4.70%	4.50%	4.70%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.60%	3.80%	3.60%	3.80%
Other Pension Plan [Member]
Defined Benefit Plan and Postretirement Plan Disclosure
Service cost for benefits earned	$ 0.3	$ 0.3	$ 0.9	$ 0.8
Interest cost on benefit obligation	0.1	0.1	0.5	0.4
Defined benefit/postretirement plan costs	$ 0.4	$ 0.4	$ 1.4	$ 1.2
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	1.70%	1.70%	1.70%	1.70%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	2.00%	2.00%	2.00%	2.00%
Covance [Member]
Defined Benefit Plan Disclosures [Line Items]
Defined contribution retirement plan cost	$ 16.3	$ 14	$ 51.6	$ 42.6

PENSION AND POSTRETIREMENT PL_3

PENSION AND POSTRETIREMENT PLANS Defined Contribution Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Non Elective Contribution	3.00%
Defined Contribution Plan, Cost	$ 17.3	$ 14.9	$ 49.1	$ 43.6
Discretionary Contribution Percentage Mininum	1.00%
Discretionary Contribution Percentage Maximum	3.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	4.50%
Covance [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 16.3	14	51.6	42.6
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (0.1)	$ 0.5	$ (0.3)	$ 1.5

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Noncontrolling interest puts	$ 15.9	$ 16.3
Fair market value of zero-coupon subordinated notes	20.3	18.8
Fair market value of senior notes	5,904.8	6,078.9
Cash Surrender Value, Fair Value Disclosure	69.7	64
Fair Value Liabilities Measured On Recurring Basis Deferred Compensation Liability	71.1	64.5
Contingent Consideration Classified as Equity, Fair Value Disclosure	16.5	16.5
Fair Value Hedges, Net	0.5
Foreign Currency Contract, Asset, Fair Value Disclosure	8.1
Level 1 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Noncontrolling interest puts	0	0
Cash Surrender Value, Fair Value Disclosure	0	0
Contingent Consideration Classified as Equity, Fair Value Disclosure	0	0
Fair Value Hedges, Net	0	0
Foreign Currency Contract, Asset, Fair Value Disclosure	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Noncontrolling interest puts	15.9	16.3
Cash Surrender Value, Fair Value Disclosure	69.7	64
Fair Value Liabilities Measured On Recurring Basis Deferred Compensation Liability	0	0
Contingent Consideration Classified as Equity, Fair Value Disclosure	0	0
Fair Value Hedges, Net	0.5	4.1
Foreign Currency Contract, Asset, Fair Value Disclosure	8.1
Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Noncontrolling interest puts	0	0
Cash Surrender Value, Fair Value Disclosure	0	0
Fair Value Liabilities Measured On Recurring Basis Deferred Compensation Liability	0	0
Contingent Consideration Classified as Equity, Fair Value Disclosure	16.5	16.5
Fair Value Hedges, Net	0	$ 0
Foreign Currency Contract, Asset, Fair Value Disclosure	$ 0

DERIVATIVE INSTRUMENTS AND HE_2

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	$ (16,100,000)	$ 8,100,000
Long-term Debt, Excluding Current Maturities	$ 6,044,600,000	6,044,600,000	$ 6,344,600,000
Debt Instrument, Basis Spread on Variable Rate	2.298%
Fair Value Hedges, Net	$ 500,000	500,000
Foreign Currency Contract, Asset, Fair Value Disclosure	$ 8,100,000	8,100,000
Minimum percentage of market price to calculated value of zero-coupon subordinated debt at which the entity is subject to contingent cash interest	120.00%
Embedded derivative, fair value	$ 0	0
Embedded derivative, impact on condensed consolidated statements of operations	0
Senior notes due 2022 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Long-term Debt, Excluding Current Maturities	500,000,000	500,000,000	500,000,000
Foreign Currency Contract, Asset, Fair Value Disclosure	6,600,000	6,600,000
Cross currency swap maturing 2022 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount	$ 300,000,000	$ 300,000,000
Senior notes due 2020 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%	4.625%
Long-term Debt, Excluding Current Maturities	$ 599,500,000	$ 599,500,000	604,100,000
Senior Long Term Notes Due2020 Member
Derivative Instruments, Gain (Loss) [Line Items]
Long-term Debt, Excluding Current Maturities	600,000,000	600,000,000
Senior notes due 2025 [Member] [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Long-term Debt, Excluding Current Maturities	1,000,000,000	1,000,000,000	1,000,000,000
Foreign Currency Contract, Asset, Fair Value Disclosure	1,500,000	1,500,000
Fair Value, Inputs, Level 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair Value Hedges, Net	500,000	500,000	$ 4,100,000
Foreign Currency Contract, Asset, Fair Value Disclosure	$ 8,100,000	$ 8,100,000

SUPPLEMENTAL CASH FLOW INFORM_3

SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Debt Conversion [Line Items]
Decrease in Capital Expenditures Incurred but not yet Paid	$ 6.9
Capital Expenditures Incurred but Not yet Paid		$ (0.4)
Cash paid during period for:
Interest	276.3	174.4
Income taxes, net of refunds	235	263.7
Disclosure of non-cash financing and investing activities:
Conversion of zero-coupon convertible debt	0.3	13.7
Fair Value of Assets Acquired	0	$ 7.3
Other Significant Noncash Transaction, Value of Consideration Given	$ 67.4

BUSINESS ACQUISITIONS (Details)

BUSINESS ACQUISITIONS (Details) - USD ($) $ / shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jul. 31, 2017	Dec. 31, 2015
Business Combination Purchase Price Allocation [Line Items]
Proforma consolidated net revenue		$ 2,747.3		$ 8,086.6
Revenues	$ 2,831.3	2,621.4	$ 8,545.9	7,563.3
Operating Income (Loss)	343.4	326.7	1,018	974.6
Other Long-term Debt	0		0		$ 57.8
Other Significant Noncash Transaction, Value of Consideration Given			67.4
Net Income (Loss) Attributable to Parent	318.8	171.5	725.8	539.3
Goodwill, Acquired During Period			49.5		1,009.8
Goodwill	$ 7,362.7		7,362.7		$ 7,400.9		$ 6,424.4
Cash payments for laboratory-related assets			257.6	216.8
Payments to Acquire Businesses, Net of Cash Acquired			$ 79.1	1,799.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents						$ 30.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables						103.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets						32.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets						57.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment						12.1
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net						735.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets						1,612.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable						45.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities						19.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Deferred Revenue						124.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent						196.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other						2.4
Business Combination, Separately Recognized Transactions, Liabilities Recognized						387.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net						1,224.5
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax		313.2		975
Business Acquisition, Pro Forma Net Income (Loss)		$ 158.1		$ 521.2
Business Acquisition, Pro Forma Earnings Per Share, Basic		$ 0		$ 0
Proforma consolidated diluted earnings per share		$ 0		$ 0
Chiltern [Member]
Business Combination Purchase Price Allocation [Line Items]
Cash paid for acquisition						1,224.5
Customer Relationships [Member]
Business Combination Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles						602
Customer Relationships [Member] | Chiltern [Member]
Business Combination Purchase Price Allocation [Line Items]
Acquired Finite-lived Intangible Assets, Useful Life	21 years
Trademarks and Trade Names [Member]
Business Combination Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles						10.6
Trademarks and Trade Names [Member] | Chiltern [Member]
Business Combination Purchase Price Allocation [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years
Software and Software Development Costs [Member] | Chiltern [Member]
Business Combination Purchase Price Allocation [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years
Technology-Based Intangible Assets [Member]
Business Combination Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles						$ 26

BUSINESS ACQUISITIONS Busines_2

BUSINESS ACQUISITIONS Business Acquisitions in the Aggregate (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Proforma consolidated net revenue		$ 2,747.3		$ 8,086.6
Other Long-term Debt	$ 0		$ 0		$ 57.8
Revenues	2,831.3	$ 2,621.4	8,545.9	7,563.3
Payments to Acquire Businesses, Net of Cash Acquired			79.1	$ 1,799.3
Goodwill, Acquired During Period			49.5		1,009.8
Goodwill	$ 7,362.7		7,362.7		$ 7,400.9	$ 6,424.4
Finite-lived Intangible Assets Acquired			$ 48.5

BUSINESS ACQUISITIONS DISPOSITI

BUSINESS ACQUISITIONS DISPOSITIONS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	$ 2.4	$ 2.2	$ 6.1	$ 10.3
Cash and cash equivalents	(892.6)		(892.6)		$ (316.6)	$ (433.6)
Accounts Receivable, Net, Current	1,536.1		1,536.1		1,531
Unbilled Contracts Receivable	320.1		320.1		316.5
Supplies inventories	233		233		227.2
Prepaid expenses and other	292.5		292.5		308.8
Property, plant and equipment, net	1,734.3		1,734.3		1,706.6
Goodwill	7,362.7		7,362.7		7,400.9		$ 6,424.4
Intangible Assets, Net (Excluding Goodwill)	3,990.9		3,990.9		4,166.1
Other assets, net	239.4		239.4		217.5
Accounts payable	497.5		497.5		573.9
Deferred Revenue, Current	901.5		901.5		793.3
Deferred Tax Liabilities, Net, Current	289.4		289.4		380.8
Deferred income taxes and other tax liabilities	899.1		899.1		875.5
Commitments and contingent liabilities	$ 343		343		376
Net assets held for sale					335
Nutritional Chemistry [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses			670
Cash and cash equivalents					(0.1)
Accounts Receivable, Net, Current					24.4
Unbilled Contracts Receivable					7.6
Supplies inventories					0.4
Prepaid expenses and other					1.2
Property, plant and equipment, net					42.3
Goodwill					170.5
Intangible Assets, Net (Excluding Goodwill)					174.7
Other assets, net					0.3
Assets Held-for-sale, Not Part of Disposal Group					421.5
Accounts payable					2.4
Deferred Revenue, Current					15.2
Deferred Tax Liabilities, Net, Current					2.6
Deferred income taxes and other tax liabilities					64.1
Commitments and contingent liabilities					2.2
Disposal Group, Including Discontinued Operation, Liabilities					$ 86.5
Covance Food Solutions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			$ 258.3
UK forensic testing services business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Income (Loss)		$ 48.9

BUSINESS SEGMENT INFORMATION _2

BUSINESS SEGMENT INFORMATION Business Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	100.00%	100.00%	100.00%	100.00%
Intercompany revenue elimination	$ (2.2)	$ (0.4)	$ (4.5)	$ (0.9)
Revenues	2,831.3	2,621.4	8,545.9	7,563.3
Operating Income (Loss)	343.4	326.7	1,018	974.6
Earnings before income taxes	499.6	266.8	1,053.8	811.3
Provision for income taxes	499.6	266.8	1,053.8	811.3
Provision for income taxes	180.6	92.5	328.1	268.6
Net earnings	319	174.3	725.7	542.7
Net income attributable to Laboratory Corporation of America Holdings	(0.2)	(2.8)	0.1	(3.4)
Nonoperating Income (Expense)	156.2	(59.9)	35.8	(163.3)
Net Income (Loss) Attributable to Parent	318.8	171.5	725.8	539.3
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (33.9)	$ (37.9)	$ (106.5)	$ (105.2)
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	62.00%	68.00%	62.00%	67.00%
Revenues	$ 1,752	$ 1,754.7	$ 5,336.3	$ 5,115.5
Operating Income (Loss)	$ 289.4	336.6	$ 929.2	982
Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	38.00%		38.00%
Revenues	$ 1,081.5	867.1	$ 3,214.1	2,448.7
Operating Income (Loss)	$ 87.9	$ 28	$ 195.3	$ 97.8

REVENUE Disaggregated Revenue T

REVENUE Disaggregated Revenue Table (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Gross	$ 322.6		$ 322.6		$ 318.2
Revenue, Remaining Performance Obligation, Amount	$ 4,199.6		$ 4,199.6
Percent of remaining performance obligations recognized as revenue in next year	39.00%		39.00%
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 10.9		$ 20.5
Contract with Customer, Liability	286.2		286.2		377.4
Capitalized Contract Cost, Amortization	0.8	$ 0.1	3.3	$ 0.3
Accrued Sales Commission	22.8		22.8		24
Liabilities, Noncurrent					7,662.4
Deferred Sales Commission	35.3		35.3		25.7
Capitalized Contract Cost, Net	12.5		12.5		1.7
Amortization of Deferred Sales Commissions	4.2	$ 3.5	12.8	$ 10.6
Unbilled Contracts Receivable	$ 320.1		$ 320.1		316.5
Percent of Revenue Contributed	100.00%	100.00%	100.00%	100.00%
Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed				20.00%
Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed				9.00%
Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	9.00%	10.00%	9.00%	10.00%
Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed				28.00%
UNITED STATES
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	83.00%	80.00%	79.00%	79.00%
CANADA
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	3.00%	3.00%	3.00%	3.00%
UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	3.00%	3.00%	3.00%	3.00%
SWITZERLAND
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	4.00%	5.00%	5.00%
Europe [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	3.00%	3.00%	3.00%
Other countries [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	5.00%	7.00%	7.00%	7.00%
LabCorp Diagnostics [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	62.00%	68.00%	62.00%	67.00%
LabCorp Diagnostics [Member] | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	18.00%	20.00%	18.00%
LabCorp Diagnostics [Member] | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	8.00%	9.00%	9.00%
LabCorp Diagnostics [Member] | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	27.00%	29.00%	26.00%
LabCorp Diagnostics [Member] | UNITED STATES
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	59.00%	65.00%	59.00%	64.00%
LabCorp Diagnostics [Member] | UNITED STATES | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	17.00%	19.00%	17.00%	19.00%
LabCorp Diagnostics [Member] | UNITED STATES | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	8.00%	9.00%	9.00%	9.00%
LabCorp Diagnostics [Member] | UNITED STATES | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	9.00%	10.00%	9.00%	10.00%
LabCorp Diagnostics [Member] | UNITED STATES | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	25.00%	27.00%	24.00%	26.00%
LabCorp Diagnostics [Member] | CANADA
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	3.00%	3.00%	3.00%	3.00%
LabCorp Diagnostics [Member] | CANADA | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	1.00%	1.00%	1.00%	1.00%
LabCorp Diagnostics [Member] | CANADA | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | CANADA | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | CANADA | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	2.00%	2.00%	2.00%
LabCorp Diagnostics [Member] | UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | UNITED KINGDOM | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | UNITED KINGDOM | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | UNITED KINGDOM | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | UNITED KINGDOM | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | SWITZERLAND
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | SWITZERLAND | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | SWITZERLAND | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | SWITZERLAND | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | SWITZERLAND | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Other countries [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Other countries [Member] | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Other countries [Member] | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
Covance Drug Development [Member]
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	$ 665.7		$ 665.7		$ 694.4
Percent of Revenue Contributed	38.00%		38.00%
Covance Drug Development [Member] | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	38.00%	32.00%	38.00%	33.00%
Covance Drug Development [Member] | UNITED STATES | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	24.00%	15.00%	20.00%	15.00%
Covance Drug Development [Member] | CANADA | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
Covance Drug Development [Member] | UNITED KINGDOM | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	3.00%	3.00%	3.00%	3.00%
Covance Drug Development [Member] | SWITZERLAND | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	4.00%	5.00%	5.00%
Covance Drug Development [Member] | Europe [Member] | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	3.00%	3.00%	3.00%
Covance Drug Development [Member] | Other countries [Member] | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	5.00%	7.00%	7.00%	7.00%