GOODWILL AND INTANGIBLE ASSETS (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Goodwill [Line Items]
Balance as of January 1	$ 3,099.4	$ 3,022.8
Goodwill acquired during the period	2,980.0	81.8
Adjustments to goodwill	(10.8)	(5.2)
Balance at end of period	6,068.6
LabCorp Diagnostics [Member]
Goodwill [Line Items]
Balance as of January 1	2,988.9
Goodwill acquired during the period	72.2
Adjustments to goodwill	(10.9)
Balance at end of period	3,050.2
Clinical diagnostics laboratory [Member]
Goodwill [Line Items]
Balance as of January 1	2,988.9	2,912.3
Goodwill acquired during the period		81.8
Adjustments to goodwill		(5.2)
Covance Drug Development [Member]
Goodwill [Line Items]
Balance as of January 1	110.5	110.5
Goodwill acquired during the period	2,907.8	0.0
Adjustments to goodwill	0.1	$ 0.0
Balance at end of period	3,018.4
Other Segments [Member]
Goodwill [Line Items]
Balance as of January 1	$ 110.5