GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Goodwill [Line Items]
Severance Costs	$ 2.7	$ 4.5
Intangible Assets, Gross (Excluding Goodwill)	4,722.1		$ 4,604.1
Balance as of January 1	6,424.4
Goodwill, Acquired During Period	58.0	398.3
Adjustments to goodwill	19.7	(176.0)
Balance at end of period	6,502.1
Finite-Lived Intangible Assets, Accumulated Amortization	1,252.8		1,203.6
Intangible Assets, Net (Excluding Goodwill)	3,469.3		3,400.5
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Balance as of January 1	3,644.8
Goodwill, Acquired During Period	56.2	398.3
Adjustments to goodwill	(1.0)	108.8
Balance at end of period	3,700.0
Covance Drug Development [Member]
Goodwill [Line Items]
Balance as of January 1	2,779.6
Goodwill, Acquired During Period	1.8	0.0
Adjustments to goodwill	20.7	$ (284.8)
Balance at end of period	2,802.1
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	3,367.3		3,275.3
Finite-Lived Intangible Assets, Accumulated Amortization	890.5		855.2
Intangible Assets, Net (Excluding Goodwill)	2,476.8		2,420.1
Patents, Licenses And Technology [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	398.1		395.3
Finite-Lived Intangible Assets, Accumulated Amortization	168.8		163.3
Intangible Assets, Net (Excluding Goodwill)	229.3		232.0
Noncompete Agreements [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	68.6		53.0
Finite-Lived Intangible Assets, Accumulated Amortization	43.4		42.1
Intangible Assets, Net (Excluding Goodwill)	25.2		10.9
Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	409.4		406.3
Finite-Lived Intangible Assets, Accumulated Amortization	148.4		141.6
Intangible Assets, Net (Excluding Goodwill)	261.0		264.7
Use Rights [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.0		10.0
Finite-Lived Intangible Assets, Accumulated Amortization	1.7		1.4
Intangible Assets, Net (Excluding Goodwill)	8.3		8.6
Canadian licenses [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	468.7		464.2
Finite-Lived Intangible Assets, Accumulated Amortization	0.0		0.0
Intangible Assets, Net (Excluding Goodwill)	$ 468.7		$ 464.2

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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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.

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