RESTRUCTURING RESERVES (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Unused facility restructuring reserves	$ (0.2)	$ 1.2
Balance, beginning of period	43.6
Restructuring charges	34.6
Reduction of prior restructuring accruals	0.2
Cash payments and other adjustments	(44.4)
Balance, end of period	14.8
Current			$ 11.1
Non-current			3.7
Total Restructuring Reserve	43.6		14.8
Employee Severance Benefits Related Restructuring Reserve Accrual Adjustment	0.4	$ 1.1
LabCorp Diagnostics [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	2.1
Restructuring charges	15.3
Reduction of prior restructuring accruals	(0.1)
Cash payments and other adjustments	(17.0)
Balance, end of period	0.3
Total Restructuring Reserve	2.1		0.3
LabCorp Diagnostics [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	7.4
Restructuring charges	6.6
Reduction of prior restructuring accruals	(0.1)
Cash payments and other adjustments	(6.4)
Balance, end of period	2.9
Total Restructuring Reserve	7.4		2.9
Covance Drug Development [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	6.5
Restructuring charges	10.9
Reduction of prior restructuring accruals	(0.5)
Cash payments and other adjustments	(11.0)
Balance, end of period	6.9
Total Restructuring Reserve	6.5		6.9
Covance Drug Development [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	27.6
Restructuring charges	1.8
Reduction of prior restructuring accruals	0.1
Cash payments and other adjustments	10.0
Balance, end of period	4.7
Total Restructuring Reserve	$ 27.6		$ 4.7