GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Goodwill [Line Items]
Severance Costs	$ 23.1	$ 33.8
Intangible Assets, Gross (Excluding Goodwill)	4,617.5		$ 4,356.0
Balance as of January 1	6,166.3	3,099.4	3,099.4
Goodwill, Acquired During Period	292.8		3,194.6
Adjustments to goodwill	(70.1)		(127.7)
Balance at end of period	6,389.0		6,166.3
Finite-Lived Intangible Assets, Accumulated Amortization	1,160.3		1,023.6
Intangible Assets, Net (Excluding Goodwill)	3,457.2		3,332.4
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Balance as of January 1	3,201.7	2,988.9	2,988.9
Goodwill, Acquired During Period	292.8		225.6
Adjustments to goodwill	47.4		(12.8)
Balance at end of period	3,541.9		3,201.7
Covance Drug Development [Member]
Goodwill [Line Items]
Balance as of January 1	2,964.6	$ 110.5	110.5
Goodwill, Acquired During Period	0.0		2,969.0
Adjustments to goodwill	(117.5)		(114.9)
Balance at end of period	2,847.1		2,964.6
Customer Relationships [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	3,257.9		3,137.8
Finite-Lived Intangible Assets, Accumulated Amortization	824.3		725.6
Intangible Assets, Net (Excluding Goodwill)	2,433.6		2,412.2
Patents, Licenses And Technology [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	412.9		309.6
Finite-Lived Intangible Assets, Accumulated Amortization	158.8		144.7
Intangible Assets, Net (Excluding Goodwill)	254.1		164.9
Noncompete Agreements [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	51.9		51.2
Finite-Lived Intangible Assets, Accumulated Amortization	40.8		37.2
Intangible Assets, Net (Excluding Goodwill)	11.1		14.0
Trade Names [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	409.6		400.9
Finite-Lived Intangible Assets, Accumulated Amortization	135.3		115.5
Intangible Assets, Net (Excluding Goodwill)	274.3		285.4
Use Rights [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	10.0		5.5
Finite-Lived Intangible Assets, Accumulated Amortization	1.1		0.6
Intangible Assets, Net (Excluding Goodwill)	8.9		4.9
Canadian licenses [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	475.2		451.0
Finite-Lived Intangible Assets, Accumulated Amortization	0.0		0.0
Intangible Assets, Net (Excluding Goodwill)	$ 475.2		$ 451.0