RESTRUCTURING AND OTHER CHARGES (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Net restructuring charges		$ 54.6	$ 48.1	$ 70.9
Restructuring charges related to severance and other employee costs		32.9	40.3	36.1
Restructuring charges related to contractual obligations associated with leased facilities and other facility related costs		24.9	11.8	18.8
Restructuring, Settlement and Impairment Provisions				20.9
Reduction in prior employee severance benefits related restructuring accruals		1.7	2.0	0.5
Reduction in prior facility related restructuring accruals		$ 1.5	2.0	4.4
Payment of legal settlement	$ 49.5
Number of years restructuring liabilities expected to be paid out over		4 years 4 months 24 days
Covance Drug Development [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charges		$ 27.9	27.6	54.1
Asset Impairment Charges			2.3
LabCorp Diagnostics [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charges		$ 26.7	$ 20.5	$ 16.8