GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Goodwill [Line Items]
Severance Costs	$ 22.5	$ 9.0
Intangible Assets, Gross (Excluding Goodwill)	4,930.1		$ 4,604.1
Balance as of January 1	6,424.4	6,202.1	6,202.1
Goodwill, Acquired During Period	141.3		398.3
Adjustments to goodwill	75.7		(176.0)
Balance at end of period	6,641.4		6,424.4
Finite-Lived Intangible Assets, Accumulated Amortization	1,308.9		1,203.6
Intangible Assets, Net (Excluding Goodwill)	3,621.2		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	139.5		398.3
Adjustments to goodwill	(5.2)		108.8
Balance at end of period	3,779.1		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	1.8		0.0
Adjustments to goodwill	80.9		(284.8)
Balance at end of period	2,862.3		2,779.6
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	3,538.7		3,275.3
Finite-Lived Intangible Assets, Accumulated Amortization	930.7		855.2
Intangible Assets, Net (Excluding Goodwill)	2,608.0		2,420.1
Patents, Licenses And Technology [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	403.9		395.3
Finite-Lived Intangible Assets, Accumulated Amortization	175.4		163.3
Intangible Assets, Net (Excluding Goodwill)	228.5		232.0
Noncompete Agreements [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	82.8		53.0
Finite-Lived Intangible Assets, Accumulated Amortization	45.2		42.1
Intangible Assets, Net (Excluding Goodwill)	37.6		10.9
Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	413.5		406.3
Finite-Lived Intangible Assets, Accumulated Amortization	155.6		141.6
Intangible Assets, Net (Excluding Goodwill)	257.9		264.7
Use Rights [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.0		10.0
Finite-Lived Intangible Assets, Accumulated Amortization	2.0		1.4
Intangible Assets, Net (Excluding Goodwill)	8.0		8.6
Canadian licenses [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	481.2		464.2
Finite-Lived Intangible Assets, Accumulated Amortization	0.0		0.0
Intangible Assets, Net (Excluding Goodwill)	$ 481.2		$ 464.2