CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]
BALANCE at Dec. 31, 2013	$ 2,491.3	$ 10.5	$ 0.0	$ 3,373.5	$ (958.9)	$ 66.2
Net earnings attributable to Laboratory Corporation of America Holdings	391.6			391.6
Other comprehensive earnings, net of tax	(25.9)					(25.9)
Other Significant Noncash Transaction, Value of Consideration Given	0.0
Issuance of common stock under employee stock plans	106.2	0.0	106.2
Surrender of restricted stock and performance share awards	(6.6)				(6.6)
Conversion of zero-coupon convertible debt	3.5	0.0	3.5
Stock compensation	35.1		35.1
Income tax benefit from stock options exercised	5.5		5.5
Purchase of common stock	(229.9)	(0.1)	(150.3)	(79.5)
BALANCE at Sep. 30, 2014	2,770.8	10.4	0.0	3,685.6	(965.5)	40.3
BALANCE at Dec. 31, 2014	2,820.5	10.4	0.0	3,786.1	(965.5)	(10.5)
Net earnings attributable to Laboratory Corporation of America Holdings	322.6			322.6
Other comprehensive earnings, net of tax	(158.0)					(158.0)
Stock Issued During Period, Shares, Acquisitions	1.5
Adjustments to Additional Paid in Capital, Other	1,761.0
Other Significant Noncash Transaction, Value of Consideration Given	1,762.5
Issuance of common stock under employee stock plans	88.9	0.1	88.8
Surrender of restricted stock and performance share awards	(10.8)				(10.8)
Stock compensation	77.7		77.7
Income tax benefit from stock options exercised	10.1		10.1
Purchase of common stock	0.0	0.0	0.0	0.0
BALANCE at Sep. 30, 2015	$ 4,913.5	$ 12.0	$ 1,937.6	$ 4,108.7	$ (976.3)	$ (168.5)