RESTRUCTURING AND OTHER SPECIAL CHARGES (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Goodwill, Acquired During Period	$ 292.8		$ 3,194.6
Restructuring Reserve	95.6		79.2
Restructuring Charges	53.8
Restructuring Reserve Settled With Cash And Other Adjustment	(32.2)
Net restructuring charges	48.6	$ 59.9
Special charge - one-time tax liability	1.1
Amortization of Debt Discount (Premium)	5.6
Restructuring charges related to severance and other employee costs	23.1	33.8
Restructuring charges related to contractual obligations associated with leased facilities and other facility related costs	30.7	27.1
Reduction in total prior restructuring accruals	(5.2)	(1.0)
Restructuring Reserve, Current	59.9
Restructuring Reserve, Noncurrent	35.7
Facility Related Restructuring Reserve Accrual Adjustment	2.4
Unused facility restructuring reserves	2.8
Special charge, wind-down of min volume contract	4.0
Business Combination, Acquisition Related Costs	7.4
Special charge, accelerated equity compensation	2.3
Special charge, accelerated equity compensation	7.4	4.3
non-cash loss on dissolution of equity investment		2.3
special charge - consulting expense		15.1
Covance Drug Development [Member]
Restructuring Cost and Reserve [Line Items]
Goodwill, Acquired During Period	0.0		2,969.0
Net restructuring charges	38.9
Covance Drug Development [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	40.1		51.5
Restructuring Charges	11.7
Restructuring Reserve Settled With Cash And Other Adjustment	(20.7)
Reduction in total prior restructuring accruals	2.4
Covance Drug Development [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	34.3		1.1
Restructuring Charges	30.0
Restructuring Reserve Settled With Cash And Other Adjustment	(3.7)
Reduction in total prior restructuring accruals	0.5
LabCorp Diagnostics [Member]
Restructuring Cost and Reserve [Line Items]
Goodwill, Acquired During Period	292.8		225.6
Net restructuring charges	9.7
LabCorp Diagnostics [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	5.8		0.1
Restructuring Charges	11.4
Restructuring Reserve Settled With Cash And Other Adjustment	(5.7)
Reduction in total prior restructuring accruals	0.0
LabCorp Diagnostics [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	15.4		26.5
Restructuring Charges	0.7
Restructuring Reserve Settled With Cash And Other Adjustment	(9.5)
Reduction in total prior restructuring accruals	(2.3)
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Other Special Charges	8.1	$ 17.0
Covance [Member]
Restructuring Cost and Reserve [Line Items]
Business Acquisition, Transaction Costs	$ 5.5		166.0
Covance [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Business Acquisition, Transaction Costs			113.4
Covance [Member] | Interest Expense [Member]
Restructuring Cost and Reserve [Line Items]
Business Acquisition, Transaction Costs			$ 52.6