GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Goodwill [Line Items]
Severance Costs	$ 16.8	$ 11.3
Intangible Assets, Gross (Excluding Goodwill)	5,546.4		$ 5,515.9
Balance as of January 1	7,360.3
Goodwill, Acquired During Period	22.1
Adjustments to goodwill	3.5
Balance at end of period	7,385.9
Finite-Lived Intangible Assets, Accumulated Amortization	1,661.5		1,604.8
Intangible Assets, Net (Excluding Goodwill)	3,884.9		3,911.1
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Balance as of January 1	3,638.8
Goodwill, Acquired During Period	7.8
Adjustments to goodwill	0.2
Balance at end of period	3,646.8
Covance Drug Development [Member]
Goodwill [Line Items]
Balance as of January 1	3,721.5
Goodwill, Acquired During Period	14.3
Adjustments to goodwill	3.3
Balance at end of period	3,739.1
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	4,135.5		4,119.4
Finite-Lived Intangible Assets, Accumulated Amortization	1,188.9		1,146.7
Intangible Assets, Net (Excluding Goodwill)	2,946.6		2,972.7
Patents, Licenses And Technology [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	449.3		447.3
Finite-Lived Intangible Assets, Accumulated Amortization	217.4		211.2
Intangible Assets, Net (Excluding Goodwill)	231.9		236.1
Noncompete Agreements [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	78.1		76.8
Finite-Lived Intangible Assets, Accumulated Amortization	55.1		53.7
Intangible Assets, Net (Excluding Goodwill)	23.0		23.1
Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	405.1		404.0
Finite-Lived Intangible Assets, Accumulated Amortization	195.6		189.1
Intangible Assets, Net (Excluding Goodwill)	209.5		214.9
Use Rights [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.8		10.8
Finite-Lived Intangible Assets, Accumulated Amortization	4.5		4.1
Intangible Assets, Net (Excluding Goodwill)	6.3		6.7
Canadian licenses [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	467.6		457.6
Finite-Lived Intangible Assets, Accumulated Amortization	0.0		0.0
Intangible Assets, Net (Excluding Goodwill)	$ 467.6		$ 457.6

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