EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Amounts attributable to Quest Diagnostics’ common stockholders:
Net income attributable to Quest Diagnostics	$ 220	$ 194
Less: Earnings allocated to participating securities	1	1
Earnings available to Quest Diagnostics’ common stockholders – basic and diluted	$ 219	$ 193
Weighted average common shares outstanding - basic	111	111
Stock options and performance share units	2	1
Weighted average common shares outstanding - diluted	113	112
Basic (in dollars per share)	$ 1.97	$ 1.74
Diluted (in dollars per share)	$ 1.94	$ 1.72
Stock options and performance share units (in shares)	0	1