RESTRUCTURING RESERVES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Cost and Reserve [Line Items]
Unused facility restructuring reserves	$ 0.1	$ 5.5	$ 0.2	$ 5.7
Balance, beginning of period			7.8
Restructuring charges			28.9
Cash payments and other adjustments			(25.2)
Balance, end of period	11.4		11.4
Current	8.9		8.9
Non-current	2.5		2.5
Total Restructuring Reserve	11.4		11.4
LabCorp Diagnostics [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period			0.3
Restructuring charges			5.2
Cash payments and other adjustments			(4.8)
Balance, end of period	0.8		0.8
Total Restructuring Reserve	0.8		0.8
LabCorp Diagnostics [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period			0.4
Restructuring charges			8.4
Cash payments and other adjustments			(8.2)
Balance, end of period	0.4		0.4
Total Restructuring Reserve	0.4		0.4
Covance Drug Development [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period			2.4
Restructuring charges			5.0
Cash payments and other adjustments			(3.1)
Balance, end of period	4.3		4.3
Total Restructuring Reserve	4.3		4.3
Covance Drug Development [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period			4.7
Restructuring charges			10.3
Cash payments and other adjustments			(9.1)
Balance, end of period	5.9		5.9
Total Restructuring Reserve	$ 5.9		$ 5.9