GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 6,502.1		$ 6,424.4	$ 6,202.1
Amortization of intangible assets	47.6	$ 44.3
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012	125.0
Estimated amortization expense, 2013	187.5
Estimated amortization expense, 2014	179.9
Estimated amortization expense, 2015	173.0
Estimated amortization expense, 2016	169.5
Estimated amortization expense, Thereafter	2,030.8
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,700.0		3,644.8	3,137.7
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 2,802.1		$ 2,779.6	$ 3,064.4