GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Jan. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Finite-Lived Intangible Assets [Line Items]
Senior Notes, Noncurrent				$ 2,900.0
Goodwill	$ 6,252.4		$ 6,191.9		$ 3,099.4
Amortization of intangible assets	44.3	$ 31.1
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012						$ 106.0
Estimated amortization expense, 2013						167.1
Estimated amortization expense, 2014						156.3
Estimated amortization expense, 2015						149.4
Estimated amortization expense, 2016						$ 143.0
Estimated amortization expense, Thereafter	2,030.8
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,240.0		3,201.7		2,988.9
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 3,012.4		$ 2,990.2		$ 110.5
Senior notes due 2045 [Member]
Finite-Lived Intangible Assets [Line Items]
Senior Notes, Noncurrent				$ 900.0