EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share, Basic and Diluted [Abstract]
Net income attributable to Quest Diagnostics	$ 99	$ 164
Less: Earnings allocated to participating securities	0	1
Net Income (Loss) Available to Common Stockholders, Basic	$ 99	$ 163
Weighted average common shares outstanding - basic	134	134
Stock options and performance share units	1	2
Weighted average common shares outstanding - diluted	135	136
Net income (in dollars per share)	$ 0.74	$ 1.22
Net income (in dollars per share)	$ 0.73	$ 1.20
Stock options	2	4