GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 5,811.7		$ 5,885.6
Goodwill	7,388.5		7,865.0
Amortization of intangible assets	62.3	$ 57.1
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012	176.6
Estimated amortization expense, 2013	231.8
Estimated amortization expense, 2014	225.9
Estimated amortization expense, 2015	222.8
Estimated amortization expense, 2016	218.2
Estimated amortization expense, Thereafter	2,299.9
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,711.2		3,721.5
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 3,677.3		$ 4,143.5