EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share, Basic and Diluted [Abstract]
Net income attributable to Quest Diagnostics	$ 195	$ 118	$ 298	$ 179
Less: Earnings allocated to participating securities	1	1	1	1
Earnings available to Quest Diagnostics' common stockholders - basic and diluted	$ 194	$ 117	$ 297	$ 178
Weighted average common shares outstanding - basic	140	144	141	144
Stock options and performance share units	2	1	2	1
Weighted average common shares outstanding - diluted	142	145	143	145
Basic (per share)	$ 1.38	$ 0.82	$ 2.10	$ 1.24
Diluted (per share)	$ 1.37	$ 0.81	$ 2.08	$ 1.23
Stock options and performance share units not included due to their antidilutive effect	0	2	2	2