EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Amounts attributable to Quest Diagnostics’ common stockholders:
Net income attributable to Quest Diagnostics	$ 229	$ 235	$ 423	$ 437
Less: Earnings allocated to participating securities	1	1	2	2
Earnings available to Quest Diagnostics’ common stockholders – basic and diluted	$ 228	$ 234	$ 421	$ 435
Weighted average common shares outstanding - basic	111	112	111	112
Stock options and performance share units	1	2	1	2
Weighted average common shares outstanding - diluted	112	114	112	114
Basic (in dollars per share)	$ 2.05	$ 2.08	$ 3.79	$ 3.88
Diluted (in dollars per share)	$ 2.03	$ 2.05	$ 3.75	$ 3.83
Stock options and performance share units (in shares)	1	0	1	0