RESTRUCTURING AND OTHER SPECIAL CHARGES (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Net restructuring charges		$ 113.9		$ 17.8	$ 21.8
Restructuring charges related to severance and other employee costs			$ 59.2	10.5	15.4
Restructuring charges related to contractual obligations associated with leased facilities and other facility related costs			55.8	8.4	9.5
Reduction in prior employee severance benefits related restructuring accruals				0.4	0.7
Reduction in prior facility related restructuring accruals			1.1	0.7	$ 2.4
Asset Impairment Charges		39.7	0.0	$ 0.0
Reduction in total prior restructuring accruals		1.1
Special charge, ST equity retention arrangement		5.4
Special charge, accelerated equity compensation		0.3
Special charge, wind-down of min volume contract		5.7
Other special charge, dissolution of equity investment		2.3
Payment of legal settlement	$ 49.5	12.2
Other special charges, non-capitalized costs		3.0
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Special charge related to write-off of certain assets and liabilities related to an investment			25.6
Covance [Member]
Restructuring Cost and Reserve [Line Items]
Business Acquisition, Transaction Costs			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
Covance Drug Development [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charges		74.7
Asset Impairment Charges		26.7
LabCorp Diagnostics [Member]
Restructuring Cost and Reserve [Line Items]
Net restructuring charges		$ 39.2