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, 2011	$ 2,503.5	$ 11.7	$ 0	$ 3,387.2	$ (940.9)	$ 45.5
Net earnings attributable to Laboratory Corporation of America Holdings	161.6			161.6
Other comprehensive earnings, net of tax	14.4					14.4
Issuance of common stock under employee stock plans	26.2	0	26.2
Surrender of restricted stock and performance share awards	(2.6)				(2.6)
Conversion of zero-coupon convertible debt	0	0	0
Stock compensation	11.8		11.8
Income tax benefit from stock options exercised	5.0		5.0
Purchase of common stock	(122.3)	(0.1)	(43.0)	(79.2)
BALANCE at Mar. 31, 2012	2,597.6	11.6	0	3,469.6	(943.5)	59.9
BALANCE at Dec. 31, 2012	2,717.4	11.3	0	3,588.5	(951.8)	69.4
Net earnings attributable to Laboratory Corporation of America Holdings	147.2			147.2
Other comprehensive earnings, net of tax	(15.6)					(15.6)
Issuance of common stock under employee stock plans	28.8	0	28.8
Surrender of restricted stock and performance share awards	(2.4)				(2.4)
Conversion of zero-coupon convertible debt	3.1
Stock compensation	11.3		11.3
Income tax benefit from stock options exercised	2.4		2.4
Purchase of common stock	(113.9)	(0.1)	(45.6)	(68.2)
BALANCE at Mar. 31, 2013	$ 2,778.3	$ 11.2	$ 0	$ 3,667.5	$ (954.2)	$ 53.8