GOODWILL AND INTANGIBLE ASSETS - SCHEDULE OF GOODWILL (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 6,202.1	$ 6,424.4	$ 6,202.1
Adjustments to goodwill	(176.0)	95.8
Goodwill, Acquired During Period	398.3	1,009.8
Goodwill [Roll Forward]
Balance as of January 1	6,202.1	6,424.4	6,202.1
Adjustments to goodwill	(176.0)	95.8
Goodwill, net		7,530.0	6,424.4
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Goodwill	3,137.7	3,644.8	3,137.7
Adjustments to goodwill	108.8	1.1
Goodwill, Acquired During Period	398.3	198.5
Goodwill [Roll Forward]
Balance as of January 1	3,137.7	3,644.8	3,137.7
Adjustments to goodwill	108.8	1.1
Goodwill, net		3,844.4	3,644.8
Covance Drug Development [Member]
Goodwill [Line Items]
Goodwill	3,064.4	2,779.6	3,064.4
Adjustments to goodwill	(284.8)	94.7
Goodwill, Acquired During Period	0.0	811.3
Goodwill [Roll Forward]
Balance as of January 1	3,064.4	2,779.6	3,064.4
Adjustments to goodwill	$ (284.8)	94.7
Goodwill, net		$ 3,685.6	$ 2,779.6

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of increase (decrease) from foreign currency translation adjustments and purchase accounting adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e961-128460

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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