GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 7,843.7		$ 7,843.7		$ 7,360.3
Amortization of intangible assets	60.2	$ 58.5	117.3	$ 120.8
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012	119.1		119.1
Estimated amortization expense, 2013	232.0		232.0
Estimated amortization expense, 2014	225.2		225.2
Estimated amortization expense, 2015	219.3		219.3
Estimated amortization expense, 2016	215.6		215.6
Estimated amortization expense, Thereafter	2,528.2		2,528.2
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,663.0		3,663.0		3,638.8
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 4,180.7		$ 4,180.7		$ 3,721.5