BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%
Total net revenues	$ 1,884	$ 1,817
Total operating income	272	279
Non-operating expenses, net	(43)	(33)
Income before income taxes and equity in earnings of equity method investees	229	246
Income tax expense	(52)	(78)
Equity in earnings of equity method investees, net of taxes	12	7
Net income	189	175
Less: Net income attributable to noncontrolling interests	12	11
Net income attributable to Quest Diagnostics	$ 177	$ 164
DIS business [Member]
Segment Reporting Information [Line Items]
Percentage of net revenues	96.00%	95.00%
Total net revenues	$ 1,803	$ 1,730
Total operating income	308	306
All other operating segments [Member]
Segment Reporting Information [Line Items]
Total net revenues	81	87
Total operating income	11	13
General corporate activities [Member]
Segment Reporting Information [Line Items]
Total operating income	$ (47)	$ (40)