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, 2015	$ 4,945.1	$ 12.0	$ 1,974.5	$ 4,223.7	$ (978.1)	$ (287.0)
Net earnings attributable to Laboratory Corporation of America Holdings	368.2			368.2
Other comprehensive earnings, net of tax	(70.4)					(70.4)
Issuance of common stock under employee stock plans	40.7	0.1	40.6
Surrender of restricted stock and performance share awards	(33.1)				(33.1)
Conversion of zero-coupon convertible debt	4.9		4.9
Stock compensation	57.6		57.6
Purchase of common stock		(12.1)	(2,077.6)	(4,591.9)
BALANCE at Jun. 30, 2016	5,313.0				(1,011.2)	(357.4)
BALANCE at Dec. 31, 2016	5,505.8	12.1	2,131.7	4,955.8	(1,012.7)	(581.1)
Net earnings attributable to Laboratory Corporation of America Holdings	380.8			380.8
Other comprehensive earnings, net of tax	196.8			0.0		196.8
Other Significant Noncash Transaction, Value of Consideration Given	31.4
Issuance of common stock under employee stock plans	46.2	0.1	31.3
Surrender of restricted stock and performance share awards					(46.2)
Conversion of zero-coupon convertible debt	12.8		12.8
Stock compensation	52.7		52.7
Purchase of common stock	(256.0)	0.2	255.8
BALANCE at Jun. 30, 2017	$ 5,878.1	$ 12.0	$ 1,972.7	$ 5,336.6	$ (1,058.9)	$ (384.3)