EARNINGS PER SHARE (Reconciliation of Basic Earnings Per Share to Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income [Abstract]
Net earnings attributable to Laboratory Corporation of America Holdings	$ 183.3
Shares [Abstract]
Net earnings, basic (in shares)	86.6	90.2	87.9	91.9
Dilutive effect of employee stock options and awards, (in shares)	0.4	0.5	0.4	0.5
Income (Loss) from Continuing Operations, Per Diluted Share	$ 2.11	$ 3.06	$ 6.19	$ 10.45
Per Share Amount [Abstract]
Net Income (Loss) Available to Common Stockholders, Diluted	$ 183.3	$ 276.9	$ 546.3	$ 965.2
Weighted Average Number of Shares Outstanding, Diluted	87.0	90.7	88.3	92.4
Income (Loss) from Continuing Operations, Per Basic Share	$ 2.12	$ 3.07	$ 6.22	$ 10.50