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, 2022	Mar. 31, 2021
Income [Abstract]
Net earnings attributable to Laboratory Corporation of America Holdings	$ 491.6	$ 769.6
Shares [Abstract]
Net earnings, basic (in shares)	93.2	97.6
Dilutive effect of employee stock options and awards, (in shares)	0.8	0.9
Per Share Amount [Abstract]
Basic earnings per common share (in dollars per share)	$ 5.27	$ 7.88
Diluted earnings per common share (in dollars per share)	$ 5.23	$ 7.82
Net Income (Loss) Available to Common Stockholders, Diluted	$ 491.6	$ 769.6
Weighted Average Number of Shares Outstanding, Diluted	94.0	98.5