BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Total net revenues	$ 1,953	$ 1,919	$ 3,844	$ 3,803
Total operating income	307	305	555	577
Non-operating expenses, net	(42)	(41)	(77)	(84)
Income from continuing operations before income taxes and equity in earnings of equity method investees	265	264	478	493
Income tax expense	(63)	(42)	(113)	(94)
Equity in earnings of equity method investees, net of taxes	17	11	30	23
Income from continuing operations	219	233	395	422
Income from discontinued operations, net of taxes	20	0	20	0
Net income	239	233	415	422
Less: Net income attributable to noncontrolling interests	13	14	25	26
Net income attributable to Quest Diagnostics	$ 226	$ 219	$ 390	$ 396
DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	96.00%	96.00%	96.00%	96.00%
Total net revenues	$ 1,872	$ 1,835	$ 3,684	$ 3,638
Total operating income	338	341	$ 618	$ 649
DIS business | Minimum
Segment Reporting Information [Line Items]
Percentage of net revenues			95.00%	95.00%
All other operating segments
Segment Reporting Information [Line Items]
Total net revenues	81	84	$ 160	$ 165
Total operating income	12	11	21	22
General corporate activities
Segment Reporting Information [Line Items]
Total operating income	$ (43)	$ (47)	$ (84)	$ (94)