CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Common Stock, Value, Outstanding		$ 12.1
Additional Paid in Capital			$ 2,131.7
Retained Earnings (Accumulated Deficit)				$ 4,969.0
Treasury Stock, Value					$ (1,012.7)
Accumulated Other Comprehensive Income (Loss), Net of Tax						$ (581.9)
BALANCE at Dec. 31, 2016	$ 5,518.2
Net earnings attributable to Laboratory Corporation of America Holdings	1,227.1	0.0	0.0	1,227.1	0.0	0.0
Other comprehensive earnings, net of tax	248.2	0.0	0.0	0.0	0.0	248.2
Issuance of common stock under employee stock plans	73.6	0.1	73.5	0.0	0.0	0.0
Net share settlement tax payments from issuance of stock to employees	(47.4)	0.0	0.0	0.0	(47.4)	0.0
Conversion of zero-coupon convertible debt	12.8	0.0	12.8	0.0	0.0	0.0
Stock compensation	109.7	0.0	109.7	0.0	0.0	0.0
Purchase of common stock	(338.1)	(0.2)	(337.9)	0.0	0.0	0.0
BALANCE at Dec. 31, 2017	6,804.1
Common Stock, Value, Outstanding	12.0	12.0
Additional Paid in Capital	1,989.8		1,989.8
Retained Earnings (Accumulated Deficit)	6,196.1			6,196.1
Treasury Stock, Value	(1,060.1)				(1,060.1)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(333.7)					(333.7)
Net earnings attributable to Laboratory Corporation of America Holdings	883.7	0.0	0.0	883.7	0.0	0.0
Other comprehensive earnings, net of tax	(129.4)	0.0	0.0	0.0	0.0	(129.4)
Issuance of common stock under employee stock plans	69.1	0.0	69.1	0.0	0.0	0.0
Net share settlement tax payments from issuance of stock to employees	(48.0)	0.0	0.0	0.0	(48.0)	0.0
Conversion of zero-coupon convertible debt	0.3	0.0	0.3	0.0	0.0	0.0
Stock compensation	91.6	0.0	91.6	0.0	0.0	0.0
Purchase of common stock	(700.0)	(0.3)	(699.7)	0.0	0.0	0.0
BALANCE at Dec. 31, 2018	6,971.4
Common Stock, Value, Outstanding	11.7	$ 11.7
Additional Paid in Capital	1,451.1		$ 1,451.1
Retained Earnings (Accumulated Deficit)	7,079.8			$ 7,079.8
Treasury Stock, Value	(1,108.1)				$ (1,108.1)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (463.1)					$ (463.1)