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
	Mar. 31, 2023	Mar. 31, 2022
Income [Abstract]
Net earnings attributable to Laboratory Corporation of America Holdings	$ 212.9	$ 491.6
Shares [Abstract]
Net earnings, basic (in shares)	88.4	93.2
Dilutive effect of employee stock options and awards, (in shares)	0.6	0.8
Per Share Amount [Abstract]
Basic earnings per common share (in dollars per share)	$ 2.41	$ 5.27
Diluted earnings per common share (in dollars per share)	$ 2.39	$ 5.23
Net Income (Loss) Available to Common Stockholders, Diluted	$ 212.9	$ 491.6
Weighted Average Number of Shares Outstanding, Diluted	89.0	94.0