BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Total net revenues	$ 1,919	$ 1,864	$ 3,803	$ 3,681
Total operating income	305	319	577	598
Non-operating expenses, net	(41)	(27)	(84)	(60)
Income before income taxes and equity in earnings of equity method investees	264	292	493	538
Income tax expense	(42)	(94)	(94)	(172)
Equity in earnings of equity method investees, net of taxes	11	9	23	16
Net income	233	207	422	382
Less: Net income attributable to noncontrolling interests	14	14	26	25
Net income attributable to Quest Diagnostics	$ 219	$ 193	$ 396	$ 357
DIS business [Member]
Segment Reporting Information [Line Items]
Percentage of net revenues	96.00%	95.00%	96.00%	95.00%
Total net revenues	$ 1,835	$ 1,776	$ 3,638	$ 3,506
Total operating income	341	347	649	653
All other operating segments [Member]
Segment Reporting Information [Line Items]
Total net revenues	84	88	165	175
Total operating income	11	17	22	30
General corporate activities [Member]
Segment Reporting Information [Line Items]
Total operating income	$ (47)	$ (45)	$ (94)	$ (85)