EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Amounts attributable to Quest Diagnostics’ common stockholders:
Net income attributable to Quest Diagnostics	$ 226	$ 225	$ 649	$ 662
Less: Earnings allocated to participating securities	1	2	3	4
Earnings available to Quest Diagnostics’ common stockholders – basic and diluted	$ 225	$ 223	$ 646	$ 658
Weighted average common shares outstanding - basic	112	112	111	112
Stock options and performance share units	1	2	1	2
Weighted average common shares outstanding - diluted	113	114	112	114
Basic (in dollars per share)	$ 2.01	$ 1.99	$ 5.80	$ 5.87
Diluted (in dollars per share)	$ 1.99	$ 1.96	$ 5.74	$ 5.79
Stock options and performance share units (in shares)	0	1	1	0