DOCUMENT AND ENTITY INFORMATION - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Jan. 31, 2016	Jun. 30, 2015
Document and Entity Information [Abstract]
Document type	10-K
Amendment flag	false
Document period end date	Dec. 31, 2015
Document fiscal year focus	2015
Document fiscal period focus	FY
Entity registrant name	QUEST DIAGNOSTICS INC
Entity central index key	0001022079
Current fiscal year end date	--12-31
Entity filer category	Large Accelerated Filer
Entity public float			$ 10.4
Entity common stock, shares outstanding		142,758,584
Entity current reporting status	Yes
Entity voluntary filers	No
Entity well-known seasoned issuer	Yes