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	164.1			164.1
Other comprehensive earnings, net of tax	28.7					28.7
Issuance of common stock for acquisition consideration	0.0	0.0	0.0
Other Significant Noncash Transaction, Value of Consideration Given	11.9
Issuance of common stock under employee stock plans	(15.1)	0.0	(11.9)
Surrender of restricted stock and performance share awards					(15.1)
Conversion of zero-coupon convertible debt	31.8
Stock compensation			31.8
Purchase of common stock		(12.0)	(2,018.2)	(4,387.8)
BALANCE at Mar. 31, 2016	5,166.5				(993.2)	(258.3)
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	192.2			192.2
Other comprehensive earnings, net of tax	54.0			0.0		54.0
Other Significant Noncash Transaction, Value of Consideration Given	27.0
Issuance of common stock under employee stock plans	(20.7)	(0.1)	(26.9)
Surrender of restricted stock and performance share awards	(12.7)				(20.7)
Conversion of zero-coupon convertible debt	27.7		12.7
Stock compensation			27.7
Purchase of common stock	(148.0)	0.1	147.9
BALANCE at Mar. 31, 2017	$ 5,650.7	$ 12.1	$ 2,051.1	$ 5,148.0	$ (1,033.4)	$ (527.1)