EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share, Basic and Diluted [Abstract]
Net income attributable to Quest Diagnostics	$ 342	$ 129	$ 521	$ 366
Less: Earnings allocated to participating securities	2	1	3	2
Earnings available to Quest Diagnostics' common stockholders - basic and diluted	$ 340	$ 128	$ 518	$ 364
Weighted average common shares outstanding - basic	144	145	144	144
Stock options and performance share units	1		1	1
Weighted average common shares outstanding - diluted	145	145	145	145
Basic (per share)	$ 2.37	$ 0.89	$ 3.61	$ 2.52
Diluted (per share)	$ 2.35	$ 0.88	$ 3.58	$ 2.51
Stock options and performance share units not included due to their antidilutive effect	2	0	2	3