BUSINESS SEGMENT INFORMATION Business Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Total net revenues	$ 2,269.9	$ 1,551.8	$ 6,260.9	$ 4,498.9
Reimbursement Revenue	47.4	0.0	118.7	0.0
Revenues	2,317.3	1,551.8	6,379.6	4,498.9
Total operating income	306.9	241.4	759.5	691.4
Non-operating expenses, net	(56.5)	(22.4)	(213.5)	(52.2)
Earnings before income taxes	250.4	219.0	546.0	639.2
Provision for income taxes	97.3	81.5	222.5	246.5
Net earnings	153.1	137.5	323.5	392.7
Less income attributable to noncontrolling interests	(0.3)	(0.3)	(0.9)	(1.1)
Net income attributable to Laboratory Corporation of America Holdings	(152.8)	(137.2)	(322.6)	(391.6)
Clinical diagnostics laboratory [Member]
Segment Reporting Information [Line Items]
Total net revenues	1,600.9	1,507.3
Total operating income	303.9	270.7
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Total net revenues			4,647.9	4,373.9
Total operating income			841.7	780.0
General corporate expenses [Member]
Segment Reporting Information [Line Items]
Total operating income	(41.8)	(36.3)	(126.0)	(105.3)
Other Segments [Member]
Segment Reporting Information [Line Items]
Total net revenues	669.0	44.5
Total operating income	44.8	7.0
Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Total net revenues			1,613.0	125.0
Reimbursement Revenue	$ 47.4	$ 0.0	118.7	0.0
Total operating income			$ 43.8	$ 16.7