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, 2014	$ 2,820.5	$ 10.4	$ 0.0	$ 3,786.1	$ (965.5)	$ (10.5)
Net earnings attributable to Laboratory Corporation of America Holdings	327.6			327.6
Other comprehensive earnings, net of tax	(269.3)					(269.3)
Issuance of common stock for acquisition consideration	1,762.5	1.5	1,761.0
Other Significant Noncash Transaction, Value of Consideration Given	88.9
Issuance of common stock under employee stock plans	(10.8)	(0.1)	(88.8)
Surrender of restricted stock and performance share awards					(10.8)
Conversion of zero-coupon convertible debt	77.7
Stock compensation	10.1		77.7
Income tax benefit from stock options exercised			10.1
BALANCE at Sep. 30, 2015	4,807.2	12.0	1,937.6	4,113.7	(976.3)	(279.8)
BALANCE at Dec. 31, 2015	4,864.0	12.0	1,974.5	4,223.0	(978.1)	(367.4)
Net earnings attributable to Laboratory Corporation of America Holdings	547.7			547.7
Other comprehensive earnings, net of tax	(10.6)			0.0		(10.6)
Other Significant Noncash Transaction, Value of Consideration Given	67.4
Issuance of common stock under employee stock plans	(33.6)	(0.1)	(67.3)
Surrender of restricted stock and performance share awards					(33.6)
Conversion of zero-coupon convertible debt	6.6
Stock compensation			81.9
BALANCE at Sep. 30, 2016	$ 5,523.4	$ 12.1	$ 2,130.3	$ 4,770.7	$ (1,011.7)	$ (378.0)