RESTRUCTURING RESERVES (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 13.4	$ 43.6	$ 54.7
Restructuring Reserve, Current	9.8
Restructuring Reserve, Noncurrent	3.6
Employee Severance Benefits Related Restructuring Reserve Accrual Adjustment	$ 1.7	2.0	0.5
Number of years restructuring liabilities expected to be paid out over	4 years 4 months 24 days
Facility Related Restructuring Reserve Accrual Adjustment	$ 1.5	2.0	4.4
Restructuring Charges	(33.1)	(52.1)
Restructuring Reserve, Accrual Adjustment	(3.2)	(4.0)
Restructuring Reserve Settled With Cash And Other Adjustment	(52.0)	(59.2)
ASC 842 Lease Adoption Implementation Impact	(32.8)
Operating Lease, Impairment Loss	24.7
LabCorp Diagnostics [Member] \| Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0.5	2.1	1.7
Restructuring Charges	(17.3)	(16.2)
Restructuring Reserve, Accrual Adjustment	(0.2)	(0.4)
Restructuring Reserve Settled With Cash And Other Adjustment	(18.7)	(15.4)
ASC 842 Lease Adoption Implementation Impact	0.0
Operating Lease, Impairment Loss	0.0
LabCorp Diagnostics [Member] \| Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	2.7	7.4	10.1
Restructuring Charges	(1.8)	(5.4)
Restructuring Reserve, Accrual Adjustment	(0.4)	(0.7)
Restructuring Reserve Settled With Cash And Other Adjustment	(8.6)	(7.4)
ASC 842 Lease Adoption Implementation Impact	(5.7)
Operating Lease, Impairment Loss	11.8
Covance Drug Development [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges		2.3
Covance Drug Development [Member] \| Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	5.5	6.5	8.3
Restructuring Charges	(15.6)	(24.1)
Restructuring Reserve, Accrual Adjustment	1.5	1.6
Restructuring Reserve Settled With Cash And Other Adjustment	(15.1)	(24.3)
ASC 842 Lease Adoption Implementation Impact	0.0
Operating Lease, Impairment Loss	0.0
Covance Drug Development [Member] \| Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	4.7	27.6	$ 34.6
Restructuring Charges	(2.0)	(6.4)
Restructuring Reserve, Accrual Adjustment	1.1	1.3
Restructuring Reserve Settled With Cash And Other Adjustment	(9.6)	$ (12.1)
ASC 842 Lease Adoption Implementation Impact	(27.1)
Operating Lease, Impairment Loss	$ 12.9

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Amount of cash paid and/or consideration other than cash paid in the period to fully or partially settle a specified, previously accrued type of restructuring cost.

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Amount of expense (reversal of expense) which increases (decreases) the restructuring reserve from an adjustment to a previously accrued restructuring liability.

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