EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share, Basic and Diluted [Abstract]
Net income attributable to Quest Diagnostics	$ 192	$ 342	$ 490	$ 521
Less: Earnings allocated to participating securities	2	2	3	3
Earnings available to Quest Diagnostics' common stockholders - basic and diluted	$ 190	$ 340	$ 487	$ 518
Weighted average common shares outstanding - basic	139	144	141	144
Stock options and performance share units	3	1	2	1
Weighted average common shares outstanding - diluted	142	145	143	145
Basic (per share)	$ 1.37	$ 2.37	$ 3.46	$ 3.61
Diluted (per share)	$ 1.34	$ 2.35	$ 3.42	$ 3.58
Stock options and performance share units not included due to their antidilutive effect	0	2	1	2