RESTRUCTURING AND OTHER SPECIAL CHARGES (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 13.0		$ 13.4
Restructuring Charges	20.4
Restructuring Reserve Settled With Cash And Other Adjustment	(32.2)
Net restructuring charges	31.8	$ 34.2
Restructuring charges related to severance and other employee costs	10.5	20.3
Other Asset Impairment Charges	8.0
Restructuring charges related to contractual obligations associated with leased facilities and other facility related costs	20.0	13.5
Employee Severance Benefits Related Restructuring Reserve Accrual Adjustment	(1.0)	(0.4)
Asset Impairment Charges	8.0
Operating Lease, Impairment Loss	10.1
Unused facility restructuring reserves	(5.7)
Reduction in total prior restructuring accruals	(6.7)
Restructuring Reserve, Current	9.4
Restructuring Reserve, Noncurrent	3.6
Covance Drug Development [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charges	20.0	18.1
Covance Drug Development [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	8.6		5.5
Restructuring Charges	7.8
Restructuring Reserve Settled With Cash And Other Adjustment	(3.8)
Asset Impairment Charges	0.0
Operating Lease, Impairment Loss	0.0
Reduction in total prior restructuring accruals	0.9
Covance Drug Development [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	2.3		4.7
Restructuring Charges	6.4
Restructuring Reserve Settled With Cash And Other Adjustment	(15.5)
Asset Impairment Charges	8.0
Operating Lease, Impairment Loss	4.0
Reduction in total prior restructuring accruals	5.3
LabCorp Diagnostics [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charges	11.8	$ 16.1
LabCorp Diagnostics [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0.1		0.5
Restructuring Charges	2.7
Restructuring Reserve Settled With Cash And Other Adjustment	(3.0)
Asset Impairment Charges	0.0
Operating Lease, Impairment Loss	0.0
Reduction in total prior restructuring accruals	(0.1)
LabCorp Diagnostics [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	2.0		$ 2.7
Restructuring Charges	3.5
Restructuring Reserve Settled With Cash And Other Adjustment	(9.9)
Asset Impairment Charges	0.0
Operating Lease, Impairment Loss	6.1
Reduction in total prior restructuring accruals	$ (0.4)