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, 2010	$ 2,466.3	$ 12.2	$ 53.9	$ 3,246.6	$ (934.9)	$ 88.5
Net earnings attributable to Laboratory Corporation of America Holdings	250.0			250.0
Other comprehensive earnings, net of tax	20.8					20.8
Issuance of common stock under employee stock plans	102.9	0.1	102.8
Surrender of restricted stock awards and performance shares awards	(6.0)				(6.0)
Conversion of zero-coupon convertible debt	36.2	0.1	36.1
Stock compensation	25.5		25.5
Income tax benefit from stock options exercised	9.9		9.9
Purchase of common stock	(325.8)	(0.3)	(155.5)	(170.0)
BALANCE at Jun. 30, 2011	2,579.8	12.1	72.7	3,326.6	(940.9)	109.3
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	314.9			314.9
Other comprehensive earnings, net of tax	3.9					3.9
Issuance of common stock under employee stock plans	43.5	0.1	43.4
Surrender of restricted stock awards and performance shares awards	(10.9)				(10.9)
Conversion of zero-coupon convertible debt	0
Stock compensation	23.7		23.7
Income tax benefit from stock options exercised	5.8		5.8
Purchase of common stock	(252.6)	(0.3)	(72.9)	(179.4)
BALANCE at Jun. 30, 2012	$ 2,631.8	$ 11.5	$ 0	$ 3,522.7	$ (951.8)	$ 49.4