BUSINESS SEGMENT INFORMATION Business Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Total net revenues	$ 1,551.8	$ 1,462.2	$ 4,498.9	$ 4,371.3
Total operating income	241.4	244.6	691.4	775.9
Non-operating expenses, net	(22.4)	(14.6)	(52.2)	(54.5)
Earnings before income taxes	219.0	230.0	639.2	721.4
Provision for income taxes	81.5	81.3	246.5	272.7
Net earnings	137.5	148.7	392.7	448.7
Less income attributable to noncontrolling interests	(0.3)	(0.4)	(1.1)	(1.2)
Net income attributable to Laboratory Corporation of America Holdings	137.2	148.3	391.6	447.5
Clinical diagnostics laboratory [Member]
Segment Reporting Information [Line Items]
Total net revenues	1,468.9	1,377.8	4,250.5	4,113.4
Total operating income	375.8	359.5	1,082.5	1,113.8
General corporate expenses [Member]
Segment Reporting Information [Line Items]
Total operating income	(155.6)	(138.9)	(455.7)	(409.6)
Other Segments [Member]
Segment Reporting Information [Line Items]
Total net revenues	82.9	84.4	248.4	257.9
Total operating income	$ 21.2	$ 24.0	$ 64.6	$ 71.7