EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share, Basic and Diluted [Abstract]
Net income attributable to Quest Diagnostics	$ 193	$ 195	$ 357	$ 298
Less: Earnings allocated to participating securities	0	1	1	1
Earnings available to Quest Diagnostics' common stockholders - basic and diluted	$ 193	$ 194	$ 356	$ 297
Weighted average common shares outstanding - basic	137	140	137	141
Stock options and performance share units	3	2	3	2
Weighted average common shares outstanding - diluted	140	142	140	143
Basic (per share)	$ 1.40	$ 1.38	$ 2.59	$ 2.10
Diluted (per share)	$ 1.37	$ 1.37	$ 2.53	$ 2.08
Stock options and performance share units not included due to their antidilutive effect	2	0	1	2