GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Goodwill [Line Items]
Severance Costs	$ 27.2	$ 23.1
Intangible Assets, Gross (Excluding Goodwill)	5,780.0		$ 4,604.1
Balance as of January 1	6,424.4	6,202.1	6,202.1
Goodwill, Acquired During Period	817.2		398.3
Adjustments to goodwill	83.5		(176.0)
Balance at end of period	7,325.1		6,424.4
Finite-Lived Intangible Assets, Accumulated Amortization	1,364.7		1,203.6
Intangible Assets, Net (Excluding Goodwill)	4,415.3		3,400.5
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Balance as of January 1	3,644.8	3,137.7	3,137.7
Goodwill, Acquired During Period	140.6		398.3
Adjustments to goodwill	(4.6)		108.8
Balance at end of period	3,780.8		3,644.8
Covance Drug Development [Member]
Goodwill [Line Items]
Balance as of January 1	2,779.6	$ 3,064.4	3,064.4
Goodwill, Acquired During Period	676.6		0.0
Adjustments to goodwill	88.1		(284.8)
Balance at end of period	3,544.3		2,779.6
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	4,297.2		3,275.3
Finite-Lived Intangible Assets, Accumulated Amortization	970.5		855.2
Intangible Assets, Net (Excluding Goodwill)	3,326.7		2,420.1
Patents, Licenses And Technology [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	455.5		395.3
Finite-Lived Intangible Assets, Accumulated Amortization	181.9		163.3
Intangible Assets, Net (Excluding Goodwill)	273.6		232.0
Noncompete Agreements [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	77.4		53.0
Finite-Lived Intangible Assets, Accumulated Amortization	47.3		42.1
Intangible Assets, Net (Excluding Goodwill)	30.1		10.9
Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	439.8		406.3
Finite-Lived Intangible Assets, Accumulated Amortization	162.7		141.6
Intangible Assets, Net (Excluding Goodwill)	277.1		264.7
Use Rights [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.0		10.0
Finite-Lived Intangible Assets, Accumulated Amortization	2.3		1.4
Intangible Assets, Net (Excluding Goodwill)	7.7		8.6
Canadian licenses [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	500.1		464.2
Finite-Lived Intangible Assets, Accumulated Amortization	0.0		0.0
Intangible Assets, Net (Excluding Goodwill)	$ 500.1		$ 464.2

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

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