BUSINESS SEGMENT INFORMATION Business Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Total net revenues	$ 2,408.1	$ 2,295.2
Intercompany revenue elimination	(0.1)	0.0
Reimbursement Revenue	38.9	72.8
Revenues	2,447.0	2,368.0
Operating Income (Loss)	332.7	299.5
Earnings before income taxes	279.7	253.6
Provision for income taxes	279.7	253.6
Provision for income taxes	87.2	89.2
Net earnings	192.5	164.4
Net income attributable to Laboratory Corporation of America Holdings	(0.3)	(0.3)
Income Loss from Continuing Operations Before Income Taxes and Minority Interest	(53.0)	(45.9)
Net Income (Loss) Attributable to Parent	192.2	164.1
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (32.9)	(38.1)
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	71.30%
Total net revenues	$ 1,717.9	1,590.6
Operating Income (Loss)	$ 309.5	274.7
Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	28.70%
Total net revenues	$ 690.3	704.6
Operating Income (Loss)	$ 56.1	$ 62.9