BUSINESS SEGMENT INFORMATION (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Percentage of net revenues from clinical testing business	90.00%	90.00%		90.00%	90.00%
Provision for special charge Medi-Cal matter			$ 236,000,000
Total net revenues	1,851,439,000	1,906,405,000		5,694,705,000	5,631,183,000
Total operating income	308,733,000	322,053,000		943,066,000	669,867,000
Non-operating expenses, net	(33,894,000)	(38,784,000)		(99,687,000)	(105,864,000)
Income from continuing operations before taxes	274,839,000	283,269,000		843,379,000	564,003,000
Income tax expense	103,340,000	101,126,000		317,111,000	256,114,000
Income from continuing operations	171,499,000	182,143,000		526,268,000	307,889,000
Income (loss) from discontinued operations, net of taxes	39,000	(250,000)		258,000	(1,131,000)
Net income	171,538,000	181,893,000		526,526,000	306,758,000
Less: Net income attributable to noncontrolling interests	8,456,000	10,045,000		26,621,000	25,628,000
Net income attributable to Quest Diagnostics	163,082,000	171,848,000		499,905,000	281,130,000
Clinical laboratory testing business [Member]
Segment Reporting Information [Line Items]
Total net revenues	1,687,512,000	1,723,102,000		5,194,591,000	5,112,215,000
Total operating income	350,878,000	348,872,000		1,081,263,000	1,025,765,000
All other operating segments [Member]
Segment Reporting Information [Line Items]
Total net revenues	163,927,000	183,303,000		500,114,000	518,968,000
Total operating income	21,201,000	24,492,000		49,111,000	47,117,000
General corporate expenses [Member]
Segment Reporting Information [Line Items]
Total operating income	(63,346,000)	(51,311,000)		(187,308,000)	(403,015,000)
Medi-Cal [Member]
Segment Reporting Information [Line Items]
Provision for special charge Medi-Cal matter			$ 236,000,000