EARNINGS (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net income attributable to Quest Diagnostics	$ 854	$ 946	$ 1,995
Less: Earnings allocated to participating securities	4	4	7
Earnings available to Quest Diagnostics’ common stockholders – basic and diluted	$ 850	$ 942	$ 1,988
Weighted average common shares outstanding - basic	112	116	125
Stock options and performance share units	1	2	3
Weighted average common shares outstanding - diluted	113	118	128
Basic (in dollars per share)	$ 7.59	$ 8.10	$ 15.85
Diluted (in dollars per share)	$ 7.49	$ 7.97	$ 15.55