GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 6,641.4		$ 6,641.4		$ 6,424.4	$ 6,202.1
Amortization of intangible assets	51.4	$ 45.3	99.0	$ 89.6
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012	92.3		92.3
Estimated amortization expense, 2013	188.9		188.9
Estimated amortization expense, 2014	181.3		181.3
Estimated amortization expense, 2015	174.0		174.0
Estimated amortization expense, 2016	170.8		170.8
Estimated amortization expense, Thereafter	2,228.7		2,228.7
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,779.1		3,779.1		3,644.8	3,137.7
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 2,862.3		$ 2,862.3		$ 2,779.6	$ 3,064.4