RESTRUCTURING RESERVES (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Amortization of Debt Discount (Premium)		$ 5.6
Balance, beginning of period	$ 82.3
Restructuring charges	66.1
Reduction of prior restructuring accruals	(1.5)
Cash payments and other adjustments	(83.6)
Balance, end of period	63.3
Current			$ 29.1
Non-current			34.2
Total Restructuring Reserve	82.3		63.3
LabCorp Diagnostics [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	7.5
Restructuring charges	8.7
Reduction of prior restructuring accruals	(0.4)
Cash payments and other adjustments	13.7
Balance, end of period	2.1
Total Restructuring Reserve	7.5		2.1
LabCorp Diagnostics [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	14.1
Restructuring charges	5.9
Reduction of prior restructuring accruals	(0.1)
Cash payments and other adjustments	(6.7)
Balance, end of period	13.2
Total Restructuring Reserve	14.1		13.2
Covance Drug Development [Member] | Severance and Other Employee Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	28.2
Restructuring charges	18.5
Reduction of prior restructuring accruals	0.9
Cash payments and other adjustments	(34.1)
Balance, end of period	11.7
Total Restructuring Reserve	28.2		11.7
Covance Drug Development [Member] | Lease and Other Facility Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	32.5
Restructuring charges	33.0
Reduction of prior restructuring accruals	0.1
Cash payments and other adjustments	29.1
Balance, end of period	36.3
Total Restructuring Reserve	$ 32.5		$ 36.3