CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
BALANCE at Dec. 31, 2019	$ 7,567.0	$ 9.0	$ 26.8	$ 7,903.6	$ (372.4)
Net earnings attributable to Laboratory Corporation of America Holdings	(317.2)	0.0	0.0	(317.2)	0.0
Other comprehensive earnings, net of tax	(145.5)	0.0	0.0	0.0	(145.5)
Issuance of common stock under employee stock plans	(26.9)	0.0	(26.9)	0.0	0.0
Surrender of restricted stock and performance share awards	(22.0)	0.0	(22.0)	0.0	0.0
Stock compensation	17.9	0.0	17.9	0.0	0.0
Purchase of common stock	(100.0)	0.0	49.6	50.4	0.0
BALANCE at Mar. 31, 2020	7,020.1	9.0	0.0	7,529.0	(517.9)
BALANCE at Dec. 31, 2019	7,567.0	9.0	26.8	7,903.6	(372.4)
Net earnings attributable to Laboratory Corporation of America Holdings	617.8
Other comprehensive earnings, net of tax	57.8
BALANCE at Sep. 30, 2020	8,239.1	9.0	80.7	8,464.0	(314.6)
BALANCE at Mar. 31, 2020	7,020.1	9.0	0.0	7,529.0	(517.9)
Net earnings attributable to Laboratory Corporation of America Holdings	231.6	0.0	0.0	231.6	0.0
Other comprehensive earnings, net of tax	68.9	0.0	0.0	0.0	68.9
Issuance of common stock under employee stock plans	(1.8)	0.0	(1.8)	0.0	0.0
Surrender of restricted stock and performance share awards	(9.5)	0.0	(9.5)	0.0	0.0
Stock compensation	39.8	0.0	39.8	0.0	0.0
BALANCE at Jun. 30, 2020	7,352.7	9.0	32.1	7,760.6	(449.0)
Net earnings attributable to Laboratory Corporation of America Holdings	703.4	0.0	0.0	703.4	0.0
Other comprehensive earnings, net of tax	134.4	0.0	0.0	0.0
Issuance of common stock under employee stock plans	(21.9)	0.0	(21.9)	0.0	0.0
Surrender of restricted stock and performance share awards	(0.5)	0.0	(0.5)	0.0	0.0
Stock compensation	27.2	0.0	27.2	0.0	0.0
BALANCE at Sep. 30, 2020	8,239.1	9.0	80.7	8,464.0	(314.6)
Retained Earnings (Accumulated Deficit)	9,402.3
BALANCE at Dec. 31, 2020	9,359.7	9.0	110.3	9,402.3	(161.9)
Net earnings attributable to Laboratory Corporation of America Holdings	769.6	0.0	0.0	769.6	0.0
Other comprehensive earnings, net of tax	(64.6)	0.0	0.0	0.0	(64.6)
Issuance of common stock under employee stock plans	(24.7)	0.0	(24.7)	0.0	0.0
Surrender of restricted stock and performance share awards	(28.1)	0.0	(28.1)	0.0	0.0
Stock compensation	28.7	0.0	28.7	0.0	0.0
Purchase of common stock	(68.5)	0.0	68.5	0.0	0.0
BALANCE at Mar. 31, 2021	10,021.5	9.0	67.1	10,171.9	(226.5)
BALANCE at Dec. 31, 2020	9,359.7	9.0	110.3	9,402.3	(161.9)
Net earnings attributable to Laboratory Corporation of America Holdings	1,824.3
Other comprehensive earnings, net of tax	(109.0)
BALANCE at Sep. 30, 2021	10,524.5	8.8	0.0	10,786.6	(270.9)
BALANCE at Mar. 31, 2021	10,021.5	9.0	67.1	10,171.9	(226.5)
Net earnings attributable to Laboratory Corporation of America Holdings	467.4	0.0	0.0	467.4	0.0
Other comprehensive earnings, net of tax	45.3	0.0	0.0	0.0	45.3
Issuance of common stock under employee stock plans	(1.9)	0.0	(1.9)	0.0	0.0
Surrender of restricted stock and performance share awards	(14.9)	0.0	(14.9)	0.0	0.0
Stock compensation	23.9	0.0	23.9	0.0	0.0
Purchase of common stock	(300.0)	0.1	78.0	221.9	0.0
BALANCE at Jun. 30, 2021	10,245.1	8.9	0.0	10,417.4	(181.2)
Net earnings attributable to Laboratory Corporation of America Holdings	587.3	0.0	0.0	587.3	0.0
Other comprehensive earnings, net of tax	(89.7)	0.0	0.0	0.0
Issuance of common stock under employee stock plans	(24.2)	0.0	(24.2)	0.0	0.0
Surrender of restricted stock and performance share awards	(1.4)	0.0	(1.4)	0.0	0.0
Stock compensation	59.0	0.0	59.0	0.0	0.0
Purchase of common stock	(300.0)	0.1	81.8	218.1	0.0
BALANCE at Sep. 30, 2021	10,524.5	$ 8.8	$ 0.0	$ 10,786.6	$ (270.9)
Retained Earnings (Accumulated Deficit)	$ 10,786.6